Structuring of copepod communities across sub-Antarctic coastal and oceanic environments during spring

Abstract

This study examines the spatial structuring of mesozooplankton communities across sub-Antarctic coastal (Beagle Channel), transitional (Staten Island), and oceanic (Burdwood Bank) environments during spring. Hydrographic (temperature and salinity), satellite-derived chlorophyll-a, and biological variables (density, biomass, size, and composition) were integrated, with emphasis on copepods as the dominant mesozooplankton group. Salinity was the environmental variable most strongly associated with copepod distribution, exhibiting a significant positive correlation with density, whereas associations with biomass, temperature, and chlorophyll-a were not significant. Four distinct copepod assemblages were identified, corresponding to regional hydrographic regimes: The inner Beagle Channel, the outer channel, the Staten Island area, and the Burdwood Bank. Copepod abundance and body size increased toward oceanic waters, suggesting enhanced secondary production linked to physical retention and upwelling processes. In contrast, coastal zones showed lower density and biomass but higher richness and evenness, likely influenced by freshwater inputs. A total of sixteen copepod species were documented, with Drepanopus forcipatus and Calanus australis widely distributed across all subregions. These species may function as ecological indicators, reflecting environmental conditions and ecosystem connectivity. Overall, the findings underscore the role of this region as a biological corridor linking coastal and oceanic systems.

Keywords:
Staten Island; Beagle Channel; Burdwood Bank; Zooplankton; Southwest Atlantic Ocean

INTRODUCTION

Mesozooplankton are a pivotal component of marine pelagic ecosystems. They mediate energy transfer from primary producers to higher trophic levels (Alcaraz and Calbet, 2003), integrate classical and microbial food web pathways (Alves et al., 2025; Calbet et al., 2001; Loeuille and Loreau, 2005; Skjoldal et al., 2000; Turner, 2004), and contribute to vertical carbon flux via fecal pellet production (Stemmann and Boss, 2012). Despite their taxonomic diversity (Skjoldal et al., 2000), mesozooplankton biomass is typically concentrated in a few dominant groups, among which copepods are particularly prominent (Verity and Smetacek, 1996). Their broad feeding spectrum (Turner, 2004) and sensitivity to hydrographic variability make them effective indicators of environmental changes (Hays et al., 2005; Mauchline, 1998; Taylor et al., 2002). Moreover, their contribution to trophic transfer and carbon export highlights their importance in the biological pump under ongoing oceanographic change (Becker et al., 2024; Calbet, 2026).

Despite their ecological relevance, baseline information on the spatial distribution and structure of mesozooplankton in the sub-Antarctic sector of the southern Patagonian shelf remains limited, particularly in transitional regions where coastal and oceanic processes interact. This study examines a longitudinal coastal-oceanic continuum encompassing the Beagle Channel (BC) (54°53’S, 66°30’-70°W), Staten Island (SI) (54°47′S-64°15′W), and Burdwood Bank (BB) (54°19’S-59°23’W) (Figure 1A), providing a natural framework to investigate how hydrographic transitions regulate copepod community assembly and ecological connectivity in sub-Antarctic systems.

Figure 1
(A) Study area location and schematic representation of regional currents (arrows), including an anticyclonic gyre contouring the bank (AC). Modified from Piola and Rivas (1997). (B) Sampling stations. Blue dots indicate stations where CTD profiles were obtained. Stations highlighted in red and numbered indicate those where both physical (CTD) and zooplankton samples were collected.

These areas differ markedly in hydrography and productivity: BC is influenced by glacial and riverine freshwater inputs (Antezana, 1999; Giesecke et al., 2021), SI represents a transitional, fjord-dominated zone (Caminos and Nullo, 1979; Hlopec et al., 2021), and BB is characterized by oceanic conditions, circulation-driven upwelling, and potential plankton retention (Matano et al., 2019; Tombesi et al., 2020). These contrasting hydrographic regimes generate distinct environmental conditions that may act as ecological filters, shaping copepod community assembly along the coastal-oceanic gradient.

The circulation of sub-Antarctic waters in this region is primarily driven by the West Wind Drift, which bifurcates around Cape Horn to form the Cape Horn and Malvinas Currents (Antezana, 1999; Ponce and Fernández, 2013). These currents influence surface hydrography and productivity patterns across the study area. Anticyclonic circulation over BB promotes the upwelling of nutrient-rich deep waters, enhancing biological productivity (Falabella, 2017; Matano et al., 2019). Within this framework, interactions among hydrography, primary productivity, and top-down processes (e.g., predation by fish larvae) may also influence zooplankton community dynamics, particularly during the productive spring-summer season.

The study area is considered a biogeographically strategic region for understanding ecological linkages between sub-Antarctic and Antarctic ecosystems (Riccialdelli et al., 2020). Although previous studies have documented seasonal increases in primary productivity and zooplankton abundance (Almandoz et al., 2011; Carrasco et al., 2023; Giesecke et al., 2021; Iachetti et al., 2021), data on taxonomic composition and spatial distribution remain limited. Spring-summer communities are typically dominated by calanoid and cyclopoid copepods, along with euphausiids, chaetognaths, siphonophores, medusae, and fish larval stages (Aguirre et al., 2012; Hamamé and Antezana, 1999; Presta et al., 2019, 2020; Sabatini, 2008; Sabatini et al., 2012, 2016; Spinelli et al., 2020).

In this context, this study aimed to assess the abundance, biomass, and distribution of mesozooplankton groups, with particular emphasis on copepods, across contrasting coastal (inner and outer BC), transitional (SI), and oceanic (BB) environments during the austral spring. Specifically, we examined associations between key environmental variables (temperature, salinity, and satellite-derived chlorophyll-a) and copepod spatial patterns, and sought to identify regional assemblages and potential ecological transitions. To our knowledge, this is the first comparative assessment of mesozooplankton communities across these three sub-Antarctic areas, providing baseline information essential for understanding ecological connectivity in the region.

Based on the contrasting hydrographic regimes across these environments, we hypothesized that copepod community assembly would vary along the coastal-oceanic continuum. Higher density, biomass, and larger body sizes were expected in the more saline oceanic waters of BB. In contrast, coastal waters influenced by freshwater inputs were expected to exhibit lower overall abundance but greater compositional heterogeneity. We further anticipated that salinity, as a proxy for water mass structure, would show a stronger association with copepod distribution than temperature or satellite-derived chlorophyll-a.

METHODS

Field sampling and oceanographic data

Sampling was conducted during the survey Área Protegida Namuncurá - Banco Burdwood aboard the oceanographic vessel Puerto Deseado, conducted during the Austral Spring of 2014 (November 4-27). Environmental data were collected at 15 sampling stations (Figure 1B). Water temperature and conductivity were measured using a CTD Rinko ASTD-102 (JFE), operating at a recording frequency of 1 Hz, to a maximum depth of 600 m. Chlorophyll-a concentration data (mg m⁻³) were obtained from NOAA PolarWatch (2024).

For descriptive and analytical purposes, stations were categorized a priori based on their geographic location and previously documented hydrographic regimes in the study area. “Inner” BC stations correspond to the western sector of the channel, characterized by stronger freshwater influence and reduced salinity, whereas “outer” stations are located toward the eastern mouth of the channel under increasing marine influence. Stations around SI were considered transitional due to their intermediate geographic location and mixed hydrographic characteristics between the coastal channel and the open-ocean domain. Stations over BB were classified as oceanic, reflecting their exposure to open sub-Antarctic waters and circulation-driven dynamics.

For zooplankton analysis, nine representative stations were selected to ensure spatial coverage of the three hydrographic domains identified among the 15 environmental stations. Samples were collected using a Bongo net (300 μm mesh size, 60 cm mouth diameter) through oblique trawls spanning the entire water column, from the bottom to the surface (Table S1). Towing speed ranged from 2.1 to 4.3 knots. A Hydrobios flowmeter was positioned at the net mouth to estimate the volume of filtered water. Subsequently, samples were preserved in 2% formaldehyde for further processing.

Zooplankton analysis

Zooplankton specimens were identified according to Boltovskoy (1999) and quantified at the lowest possible taxonomic level (species level for copepods) using a Cambridge stereoscope and an Olympus BX61 optical microscope. Each sample was diluted to a volume of 500 ml. Due to the high abundance, quantification was performed by taking 10 ml aliquots (representing 10% of the total volume) after homogenization using an aerator. With the total number of specimens of each taxon and the filtered volume known, density was estimated and expressed as individuals per cubic meter (ind. m⁻³). Biomass estimation was based on individual measurements using the Zeiss SV 8 stereoscope integrated with a Leica Image Processor (LAS 1.8.0). Copepod volume (ml) was calculated according to Warwick and Gee (1984). Wet weight (µg) was determined following Riemann et al. (1990), applying a correction factor of 0.3 to account for weight loss due to formalin preservation (Böttger-Schnack, 1985). Dry weight was estimated as 22.5% of the corrected wet weight (Gradinger et al., 1999), and carbon concentration was assumed to represent 40% of the dry biomass (Feller and Warwick, 1988). Individual biomass (µg C m⁻³) was obtained by calculating the ratio between carbon and the filtered volume, adjusted to the size of the selected sample. Finally, extrapolation was performed to estimate the total biomass for each sample.

Data analysis

Chlorophyll-a data were processed using QGIS Development Team (2024). Spatial distribution maps of environmental variables were generated using Ocean Data View (Schlitzer and Reiner, 2023). All statistical analyses were conducted in RStudio (R Core Team, 2024). Figures were subsequently edited in Inkscape (Inkscape Project, 2024).

Environmental parameters were compared using a two-factor comparison of means, based on a simple linear regression. Data from BC and SI were pooled (BC-SI) to address data availability constraints and enhance statistical robustness, while data from BB were analyzed separately.

Spatial distribution of copepod density and biomass were visualized using bubble maps generated in R with the packages rnaturalearth (Massicotte and South, 2023), rnaturalearthdata (South et al., 2024a), and rnaturalearthhires (South et al., 2024b) for geographic data. Spearman’s correlation coefficient was used to assess associations between environmental variables and copepod density and biomass.

The Kruskal-Wallis test was applied to evaluate differences in copepod size distribution among stations (Gómez-Gómez et al., 2003). Pairwise comparisons were performed using Dunn’s test, with p-values adjusted by the Bonferroni method to control for Type I errors.

Ecological diversity indices were calculated for copepod species to evaluate changes in their community structure. The Shannon-Weaver diversity index (H’) (Shannon, 1948) was used to estimate copepod diversity, the Margalef index (d) (Margalef, 1973) was applied to assess species richness, and Pielou’s index (J’) (Pielou, 1969) was used to estimate sample evenness.

A redundancy analysis (RDA) based on Hellinger-transformed species density data was conducted to examine the influence of environmental variables on copepod species distribution, using the vegan package (Oksanen et al., 2024).

Hierarchical agglomerative clustering was conducted using the Bray-Curtis similarity index (Bray and Curtis, 1957) with group-average linkage. Copepod assemblages were defined using a dissimilarity threshold of 0.7, enabling the identification of ecologically meaningful clusters. Additionally, non-metric multidimensional scaling (NMDS) based on Bray-Curtis dissimilarity was performed as a complementary approach to the clustering dendrogram.

RESULTS

Oceanographic features

Sea surface temperatures increased towards the mouth of the channel, reaching a maximum of 7.45°C. In contrast, temperature decreased at SI and continued to decline toward BB, where a minimum of 5.34°C was recorded. The mean temperature in the BC-SI group was significantly higher than in BB (t = -8.739, p < 0.05).

Surface salinity showed a gradual eastward increase, with maximum values of 34.05 at BB and minimum values of 30.98 at BC (t = 3.468, p < 0.05). Chlorophyll-a concentration peaked in the inner BC (1.38 mg m⁻³) and declined eastward (0.24 mg m⁻³) at BB. Mean chlorophyll-a concentration was significantly higher in the BC-SI group compared to BB (t = -2.714, p < 0.05) (Figure 2).

Figure 2
Spatial distribution of surface temperature (°C), salinity, and chlorophyll-a concentration (mg m^-3). Stations are represented by black dots.

Zooplankton composition

A total of 22 zooplankton groups were identified in the study area (Table S2). Copepods were the dominant group in terms of density, accounting for approximately 60% of total absolute density. The second most abundant group was appendicularians, which were consistently present across most of the study area. In contrast to BC and SI, higher abundances of euphausiids and ichthyoplankton were observed at BB, where both fish eggs and larvae were detected (Figure 3).

Figure 3
Density distribution (ind m^-3) of Copepoda, Appendicularia, Euphausiacea, and Ichthyoplankton (eggs and larvae). Low-density taxa were grouped as “Others.” Dashed lines separate the Beagle Channel (BC), Staten Island (SI), and Burdwood Bank (BB).

Beyond these dominant taxa, a diverse array of additional groups was recorded across the study area (Table S2). Nauplii, zoeae, polychaete larvae, cladocerans, and ctenophores were detected at multiple stations. Ostracods were found exclusively around SI, whereas chaetognaths appeared only at BB and at the southern station near SI. Euphausiid larval stages (calyptopis and furcilia), as well as gastropods and amphipods, were observed both at the mouth of BC and around SI. In BB, medusozoans and larvae of brachyurans, anomurans, and actinula were also recorded.

The lowest copepod density was observed in the inner BC (station 34), with 4 ind m^-3. At the mouth of the channel, values increased to a maximum of 385 ind m^-3 at SI (station 25), followed by a decline north of the island. In contrast, densities at BB were substantially higher, reaching a maximum of 628 ind m^-3 at station 11 (Figure 4A). Spearman’s correlation analysis showed that copepod density was significantly positively associated with salinity (ρ = 0.80, p < 0.05). Conversely, temperature exhibited a moderate but non-significant negative correlation (ρ = -0.65, p = 0.06), while chlorophyll-a showed a weak, non-significant association (ρ = -0.183, p > 0.05).

The highest calanoid copepod biomass was recorded in the inner BB, reaching up to 8196 μg C m^-3. In contrast, outer stations in this area exhibited notably lower values. Along BC, biomass followed a variable pattern. It was lowest in the inner zone (86.80 μg C m^-3), increased at the following station, declined again, and then peaked near SI, reaching 7584.85 μg C m^-3 (Figure 4B). Spearman’s correlations between biomass and environmental variables showed a positive association with salinity (ρ = 0.433) and a weak negative correlation with temperature (ρ = -0.217) and chlorophyll-a (ρ = -0.167); however, none of these relationships were statistically significant.

Figure 4
Spatial distribution of copepod density (ind m^-3) (A) and biomass (μg C m^-3) (B) across sub-Antarctic coastal (Beagle Channel), transitional (Staten Island), and oceanic (Burdwood Bank) environments.

Copepod Size and diversity

Copepods showed notable size variation among study areas (Figure 5). The largest individuals were found at BB, particularly at stations 10 and 13, with mean sizes of 2101.37 ± 155.95 μm and 2082.13 ± 176.57 μm, respectively. In contrast, the smallest specimens were recorded at BC (station 27: 954.38 ± 31.36 μm) and south of SI (station 23: 982.79 ± 63.56 μm). Statistical analysis revealed significant differences among stations (Kruskal-Wallis test followed by Dunn’s test, p < 0.05). Stations at BB (group “c”) differed significantly from those at BC and SI (group “a”), showing intermediate groupings (“bc” and “ab”). Furthermore, copepod density and biomass were strongly and positively correlated (ρ = 0.8, p < 0.05), indicating that stations with higher densities were associated with larger mean body sizes.

Figure 5
Size distribution of copepods along sub-Antarctic coastal (Beagle Channel [BC]), transitional (Staten Island [SI]), and oceanic (Burdwood Bank [BB]) environments. Letters “a,” “b,” and “c” indicate significant differences (p < 0.05) among stations (Dunn’s test). Stations sharing a letter (e.g., “ab”) are not significantly different from each other.

The copepod community was dominated by calanoids, which exhibited the highest densities across the study area. Cyclopoids were the second most abundant group, although their values were considerably lower. A total of 16 copepod species were identified, including 14 calanoids belonging to the families Eucalanidae, Calanidae, Centropagidae, and Clausocalanidae, and two cyclopoids from the family Oithonidae.

Centropages brachiatus was restricted to BC, while Clausocalanus brevipes was recorded from the mouth of the channel and extended into other areas. Ctenocalanus citer and Clausocalanus laticeps were widely distributed throughout BC and SI, whereas Calanoides patagoniensis was exclusively found at the channel mouth. Calanus propinquus and Subeucalanus longiceps showed a localized distribution in the northern sector of SI, and Rhincalanus nasutus was detected both around SI and in the inner BC. In the latter, Microcalanus pygmaeus was found exclusively.

Several species were concentrated in the BB, including Calanus simillimus, Ctenocalanus vanus, Neocalanus tonsus, Oithona similis, and Oithona atlantica, which were also observed in the northern area of SI. Finally, Calanus australis and Drepanopus forcipatus were recorded across all three study areas (Figure 6). The highest Margalef values were observed at station 34 (3.46, inner BC), indicating high species richness in relation to abundance, while the remaining stations showed values below 1.5. Shannon diversity ranged from 1.15 to 1.87, with the highest values recorded at station 25 (south of SI). Evenness (Pielou’s index) also peaked at station 25 (0.90), suggesting a more balanced community structure (Table 1).

Figure 6
Percentage contribution of copepod species to total density along the sub-Antarctic coastal (Beagle Channel [BC]), transitional (Staten Island [SI]), and oceanic (Burdwood Bank [BB]) environments.

Table 1
Values of the Margalef richness index (d), Shannon-Wiener diversity index (H´), and Pielou’s evenness index (J´) across sampling stations along the sub-Antarctic coastal (Beagle Channel), transitional (Staten Island), and oceanic (Burdwood Bank) environments.

Area	Station	d	H´	J´
Beagle Channel	34	3.46	1.53	0.86
	29	0.65	1.15	0.83
	27	0.98	1.56	0.87
Staten Island	25	1.18	1.87	0.90
	23	1.07	1.56	0.87
NMPA-BB	9	0.65	1.15	0.83
	10	1.27	1.27	0.58
	11	1.06	1.53	0.74
	13	1.10	1.53	0.68

The RDA analysis revealed that environmental variables explained 56% of total variability in copepod species density in the studied sub-Antarctic region (R² = 0.56) (Figure 7). The first ordination axis (RDA1) accounted for 58.84% of the explained variance and was primarily influenced by a temperature-salinity gradient. The second axis explained 12.38% of the variance and was mainly associated with chlorophyll-a concentration and, to a lesser extent, salinity. Sampling sites from BC and SI were grouped under relatively warmer and less saline conditions, where C. brachiatus reached its highest densities. In contrast, colder and more saline waters characterized BB, where D. forcipatus was predominantly found.

Figure 7
Redundancy analysis (RDA) based on Hellinger-transformed copepod species densities (yellow squares) at sampling stations from the Beagle Channel (blue), Staten Island (red), and Burdwood Bank (green). Environmental variables included temperature (Temp), salinity (Sal), and satellite-derived chlorophyll-a concentrations (Chi a) as explanatory variables.

Consistent with the RDA results, both the density-based Bray-Curtis dendrogram and NMDS ordination (stress < 0.05) identified four distinct copepod assemblages across the study area (Figure 8). The first cluster consisted solely of station 34, located within the inner BC. The second group comprised stations from the outer section of the channel. The third cluster included all stations from SI, whereas the fourth encompassed all stations from BB.

Figure 8
Hierarchical cluster analysis using Bray-Curtis dissimilarity and non-metric multidimensional scaling (NMDS) based on copepod species density. Both analyses were performed using log(x+1) transformed densities to account for both dominant and rare species. The dendrogram identified four distinct groupings: Inner Beagle Channel (34), outer Beagle Channel (27 and 29), Staten Island (23 and 25), and Burdwood Bank (9, 10, 11, and 13).

DISCUSSION

This study revealed a clear spatial structuring of mesozooplankton communities across sub-Antarctic coastal, transitional, and oceanic environments, closely associated with hydrographic differences along the coastal-oceanic continuum. BC was characterized by warmer, less saline waters influenced by riverine and glacial inputs (Adami and Gordillo, 1999; Carrasco et al., 2023), whereas BB exhibited colder, more saline oceanic conditions (Sabatini et al., 2016; Spinelli et al., 2020). These contrasts were reflected in copepod density, biomass, and body size, which increased toward oceanic waters. Concurrently, species richness and evenness were higher in coastal and transitional sectors, as consistently supported by multivariate analyses.

The spatial patterns observed in copepod density and biomass are likely governed by a combination of abiotic and biotic drivers, as widely reported in previous studies (Boltovskoy, 1981; Guichard and Bourget, 1998; Irigoien et al., 2011; Rakhesh et al., 2006; Sabatès et al., 1989). In our study, salinity was the environmental variable most strongly associated with copepod distribution, exhibiting a significant positive correlation with density. However, rather than acting as a direct ecological driver, salinity in this system likely reflects broader hydrographic differences among water masses along the coastal-oceanic continuum. Specifically, the salinity gradient integrates the influence of freshwater inputs, stratification, circulation patterns, and oceanic connectivity, all of which may shape copepod community structure. The lowest recorded copepod densities were observed in the inner BC, where the confluence of riverine and glacial freshwater inputs results in reduced salinity.

These conditions may impose physiological constraints on oceanic copepod species, which generally perform better in high-salinity environments (Mauchline, 1998). Moreover, low salinity can influence phytoplankton and microbial community structure, potentially affecting food quality and availability (Guinder et al., 2010). Predation pressure from fish larvae associated with Macrocystis pyrifera kelp forests may also influence copepod densities in this sector (Alonso et al., 2024; Álvarez-Colombo et al., 2011; Bruno et al., 2018), although such top-down effects were not directly evaluated in this study.

Consistently, the clear separation of copepod assemblages along the salinity gradient highlights the importance of water mass structure and associated hydrographic regimes in this sub-Antarctic system. In this context, salinity should be interpreted primarily as an indicator of broader hydrographic differences rather than as an isolated causal factor. Similar patterns have been documented in shelf and coastal environments where hydrographic gradients, particularly salinity, structure mesozooplankton assemblages and define biogeographic compartments (Irigoien et al., 2011; Rakhesh et al., 2006; Sabatini et al., 2016). Rather than acting solely as a physiological constraint, salinity likely integrates multiple hydrographic processes, including freshwater influence in the inner channel and circulation-driven retention over BB. Such mechanisms may regulate both species occurrence and relative dominance, consistent with known salinity tolerances and life-history strategies of calanoid copepods (Mauchline, 1998).

Conversely, the highest copepod densities and biomasses were observed at BB, characterized by colder, more saline, and oceanographically dynamic conditions. Such features are often associated with enhanced nutrient availability and vertical structure, which may favor phytoplankton growth and secondary production (Longhurst, 2010). Physical processes such as anticyclonic circulation and topographic upwelling (Matano et al., 2019) may facilitate plankton retention and aggregation, potentially favoring accumulation of larger copepods. However, as these mechanisms were not directly measured, they should be regarded as plausible explanatory hypotheses consistent with the observed spatial patterns.

The strong positive correlation between copepod density and biomass indicates that not only were individuals more numerous, but larger copepods were also dominant, suggesting enhanced trophic transfer and energy flow in oceanic environments (Calbet and Saiz, 2005).

Although satellite-derived chlorophyll-a was not significantly correlated with copepod density in this dataset, previous studies highlight the importance of in situ productivity and food-web structure in regulating copepod distribution. At BC, copepod patterns were significantly influenced by fluorescence-based chlorophyll-a, picoeukaryote abundance, and stratification (Carrasco et al., 2023). Moreover, satellite chlorophyll estimates may underestimate subsurface or transient blooms in optically complex waters (Becker et al., 2024) and fail to capture prey-size structure and food quality, which are key determinants of copepod nutritional condition (Calbet and Saiz, 2005; Vargas et al., 2009). The spatial heterogeneity observed across the sub-Antarctic gradient likely reflects interactions between hydrography and trophic structure, reinforcing the notion that copepod assemblages are regulated by integrated environmental processes rather than by surface chlorophyll concentration alone.

Calanoid copepods constituted the dominant component of the mesozooplankton assemblage throughout the study area, with appendicularians ranking second, consistent with previous spring-summer surveys in the region (Aguirre et al., 2012; Hamamé and Antezana, 1999; Presta et al., 2019, 2020; Sabatini, 2008; Sabatini et al., 2012, 2016; Spinelli et al., 2020). Regional variation in appendicularian composition further reflected hydrographic contrasts along the gradient (Alves et al., 2025; Presta et al., 2023), with species distribution patterns differing among coastal, transitional, and oceanic environments.

A distinct compositional shift was observed concerning euphausiids. Larval stages (nauplii, calyptopis, and furcilia) occurred at BC and around SI, whereas adult euphausiids were exclusively detected at BB, including Euphausia vallentini and Euphausia lucens (Spinelli et al., 2020), reinforcing the oceanic character of this area and corroborating previous observations (Brazuna, 2020; Carrasco et al., 2023). These compositional differences likely reflect biogeographic structuring driven by contrasting hydrographic regimes, whereby coastal environments favor smaller calanoids and appendicularians adapted to higher concentrations of micro- and nanoplankton (Hopcroft et al., 2001).

Copepod species composition exhibited distinct regional patterns. At BC, a longitudinal succession was observed, with C. australis dominating the inner sector, C. brevipes prevailing in the middle zone, and C. brachiatus increasing toward the channel mouth. This distribution contrasts with the dominance of O. similis, C. citer, and D. forcipatus reported during the spring seasons of 2006-2007 (Aguirre et al., 2012; Presta et al., 2020), as well as the prevalence of M. pygmaeus and C. brachiatus in autumn 2006 (Presta et al., 2020). The patterns observed in this study differ from those in previous records, potentially due to methodological differences (e.g., mesh size), but may also reflect variations in environmental conditions and water quality.

A comparable spatial structure was observed around SI, where C. citer dominated the northern area, while D. forcipatus prevailed in the south area. Notably, D. forcipatus also emerged as the dominant species at BB. Both C. australis and D. forcipatus exhibited a ubiquitous distribution across all regions (Figure S1), highlighting their ecological flexibility. Although their wide occurrence along Argentinian and Chilean shelves has been documented (Fernández-Severini and Hoffmeyer, 2005; Sabatini, 2008; Sabatini et al., 2000, 2001), our findings provide new insights into their spatial partitioning along a hydrographic continuum. Given their consistent dominance and extensive distribution, these copepods may serve as ecological indicators of connectivity between coastal and oceanic sub-Antarctic systems (Antacli et al., 2014; Cornils et al., 2007).

Taken together, these results demonstrate a marked spatial structuring of copepod species across coastal and oceanic environments, shaped by both environmental gradients and biological processes. Overall, copepod assemblage structure was primarily associated with hydrographic differences across the study area, with salinity providing the strongest signal, whereas temperature and satellite-derived chlorophyll-a played secondary roles. This pattern highlights the sensitivity of copepod communities to hydrographic variability across the coastal-oceanic continuum.

Although biomass was estimated using widely accepted conversion factors and preservation corrections, some degree of uncertainty is inherent to such calculations, including interspecific variability in carbon content, ontogenetic differences, and potential shrinkage due to formalin fixation. These sources of variability may affect absolute biomass estimates; however, the consistent application of the same methodological approach across stations ensures that the relative spatial patterns described here remain robust for comparative purposes.

For certain statistical comparisons, data from BC and SI were pooled to increase analytical robustness. Although this approach improved statistical stability, it may have reduced the resolution of fine-scale spatial differences between these areas. Nevertheless, multivariate analyses conducted at the station level (RDA, clustering, NMDS) consistently distinguished transitional patterns associated with SI, supporting the reliability of the broader spatial structuring identified.

This study represents a single seasonal snapshot of austral spring conditions. While this temporal scope prevents the assessment of intra-annual or inter-annual variability, the results provide a baseline for understanding mesozooplankton spatial structuring in heterogeneous sub-Antarctic environments. Consequently, the ecological mechanisms discussed here, including hydrographic retention and potential trophic controls, should be interpreted as plausible explanatory processes consistent with the observed patterns rather than as directly tested drivers. Future multi-seasonal assessments will be necessary to evaluate temporal variability and long-term ecosystem responses to climate forcing.

CONCLUSION

This study provides new insights into the spatial structuring of spring mesozooplankton communities across contrasting sub-Antarctic coastal, transitional, and oceanic environments, with salinity emerging as the environmental variable most strongly associated with copepod distribution. Four distinct copepod assemblages were identified, reflecting regional differences in hydrographic conditions along the coastal-oceanic continuum. Copepod density, biomass, and body size increased toward oceanic waters, consistent with physical retention and upwelling dynamics, whereas coastal and transitional zones exhibited lower density and biomass but higher richness and evenness, likely associated with freshwater influence and environmental heterogeneity. The widespread dominance of Drepanopus forcipatus and Calanus australis underscores their role as key species and potential ecological indicators of connectivity between contrasting environments. Overall, these findings highlight the role of hydrographic variability in structuring sub-Antarctic zooplankton communities and reinforce the function of this region as a biological corridor linking coastal and oceanic systems.

Acknowledgments

The authors thank the leaders and coordinators of the cruises throughout the years, as well as Maria Laura Presta and everyone who participated in the oceanographic surveys for their cooperation during sample collection and preparation.

Supplementary material

Supplementary material available at https://zenodo.org/records/20546218

Supplementary Material 1

Supplementary Material 1 Supplementary Material 1

Supplementary Material 2

Supplementary Material 2

Supplementary Material 3

Supplementary Material 3

Data availability statement:

All data are available from the corresponding author upon reasonable request.

REFERENCES

• Adami, M. L. & Gordillo, S. 1999. Structure and dynamics of the biota associated with Macrocystis pyrifera (Phaeophyta) from the Beagle Channel, Tierra del Fuego, Scientia Marina, 63(S1), 183-191. DOI: https://doi.org/10.3989/scimar.1999.63s1183
  » https://doi.org/10.3989/scimar.1999.63s1183
• Aguirre, G. E., Capitanio, F. L., Lovrich, G. A. & Esnal, G. B. 2012. Seasonal variability of metazooplankton in coastal sub-Antarctic waters (Beagle Channel). Marine Biology Research, 8(4), 341-353. DOI: https://doi.org/10.1080/17451000.2011.627922
  » https://doi.org/10.1080/17451000.2011.627922
• Alcaraz, M. & Calbet, A. 2003. Zooplankton Ecology. In: Duarte, C. M. & Helgueras, A. L. (Ed.). Marine Ecology (pp. 295-318). Paris: Unesco-EOLSS.
• Almandoz, G. O., Hernando, M. P., Ferreyra, G. A., Schloss, I. R. & Ferrario, M. E. 2011. Seasonal phytoplankton dynamics in extreme southern South America (Beagle Channel, Argentina). Journal of Sea Research, 66(2), 47-57. DOI: https://doi.org/10.1016/j.seares.2011.03.005
  » https://doi.org/10.1016/j.seares.2011.03.005
• Alonso, V. A. G., Franco, B. C., Palma, E. D., Pájaro, M. & Capitanio, F. L. 2024. Integration of empirical and modelled data unravels spatiotemporal distribution and connectivity patterns of Fuegian sprat early life stages. Marine Ecology Progress Series, 731, 27-49. DOI: https://doi.org/10.3354/meps14329
  » https://doi.org/10.3354/meps14329
• Álvarez-Colombo, G., Dato, C., Macchi, G. J., Palma, E., Machinandiarena, L., Christiansen, H. E., Betti, P., Derisio, C., Martos, P., Castro-Machado, F., Brown, D., Ehrlich, M., Mianzan, H. & Acha, E. M. 2011. Distribution and behavior of Argentine hake larvae: evidence of a biophysical mechanism for self-recruitment in northern Patagonian shelf waters. Ciencias Marinas, 37(4B), 633-657. DOI: https://doi.org/10.7773/cm.v37i4B.1777
  » https://doi.org/10.7773/cm.v37i4B.1777
• Alves, N., Spinelli, M. L., Martín, J., Malits, A. & Capitanio, F. L. 2025. Ecological role of pelagic appendicularians in sub-Antarctic coastal and oceanic waters of the Southwest Atlantic Ocean. Polar Biology, 48(1), 28. DOI: https://doi.org/10.1007/s00300-024-03331-z
  » https://doi.org/10.1007/s00300-024-03331-z
• Antacli, J. C., Sabatini, M. E., Silva, R. I., Hernández, D. R., Jaureguizar, A. J. & Akselman, R. 2014. Feeding and reproductive activity of the copepods Drepanopus forcipatus AND Calanus australis during late summer on the southern Patagonian shelf (Argentina, 47°-55°S). Brazilian Journal of Oceanography, 62(4), 295-314. DOI: https://doi.org/10.1590/S1679-87592014073406204
  » https://doi.org/10.1590/S1679-87592014073406204
• Antezana, T. 1999. Hydrographic features of Magellan and Fuegian inland passages and adjacent Subantarctic waters. Scientia Marina, 63(S1), 23-34. DOI: https://doi.org/10.3989/scimar.1999.63s123
  » https://doi.org/10.3989/scimar.1999.63s123
• Becker, E. C., Macedo-Soares, L. C. P., Marcolin, C. R., Brandão, M. C., Stemmann, L., Mazzocchi, M. G. & Freire, A. S. 2024. Oceanographic features boost latitudinal patterns in copepod body size distribution in the South Atlantic. Limnology and Oceanography, 69(11), 2668-2679. DOI: https://doi.org/10.1002/lno.12694
  » https://doi.org/10.1002/lno.12694
• Boltovskoy, D. 1999. South Atlantic Zooplankton Vol. 1. Leiden: Backhuys Publishers.
• Boltovskoy, D. 1981. Atlas de zooplancton del Atlántico sudoccidental y métodos de trabajo con el zooplancton marino Mar del Plata, Instituto Nacional de Investigación y Desarrollo Pesquero - INIDEP.
• Böttger-Schnack, R. 1985. Untersuchungen zur Verteilung der kleinen Metazoa im Plankton des Roten Meeres, unter besonderer Berücksichtigung cyclopoider und harpacticoider Copepoden (Ph. D. Thesis). Hamburg: Universität Hamburg.
• Bray, J. R. & Curtis, J. T. 1957. An ordination of the upland forest communities of Southern Wisconsin. Ecological Monographs, 27(4), 325-349. DOI: https://doi.org/10.2307/1942268
  » https://doi.org/10.2307/1942268
• Brazuna, P. 2020. Ecología de eufáusidos: densidad, diversidad y rol trófico en el AMP Namuncurá/ Banco Burdwood (Tesis). Buenos Aires: Universidad de Buenos Aires.
• Bruno, D. O., Victorio, M. F., Acha, E. M. & Fernández, D. A. 2018. Fish early life stages associated with giant kelp forests in sub-Antarctic coastal waters (Beagle Channel, Argentina). Polar Biology, 41(2), 365-375. DOI: https://doi.org/10.1007/s00300-017-2196-y
  » https://doi.org/10.1007/s00300-017-2196-y
• Calbet, A., Landry, M. R. & Nunnery, S. 2001. Bacteria-flagellate interactions in the microbial food web of the oligotrophic subtropical North Pacific. Aquatic Microbial Ecology, 23, 283-292. DOI: https://doi.org/10.3354/ame023283
  » https://doi.org/10.3354/ame023283
• Calbet, A. & Saiz, E. 2005. The ciliate-copepod link in marine ecosystems. Aquatic Microbial Ecology, 38, 157-167. DOI: https://doi.org/10.3354/ame038157
  » https://doi.org/10.3354/ame038157
• Calbet, A. 2026. Roles of microzooplankton in the biological carbon pump. Progress in Oceanography, 243, 103700. DOI: https://doi.org/10.1016/j.pocean.2026.103700
  » https://doi.org/10.1016/j.pocean.2026.103700
• Caminos, R. & Nullo, F. 1979. Descripción geológica de la Hoja 67 e, Isla de los Estados. Territorio Nacional de Tierra del Fuego, Antártida, e Islas del Atlántico Sur. Carta Geológico-Económica de la República Argentina. Escala 1:200.000. Boletín 175, 63 p. Buenos Aires, Servicio Geológico Nacional.
• Carrasco, C. V., Boy, C. C., Malits, A., Martín, J. & Capitanio, F. L. 2023. Spatial distribution of zooplankton in the Beagle Channel in relation to hydrographic and biological drivers in different seasons. Journal of Marine Systems, 240, 103880. DOI: https://doi.org/10.1016/j.jmarsys.2023.103880
  » https://doi.org/10.1016/j.jmarsys.2023.103880
• Cornils, A., Schnack-Schiel, S. B., Böer, M., Graeve, M., Struck, U., Al-Najjar, T. & Richter, C. 2007. Feeding of Clausocalanids (Calanoida, Copepoda) on naturally occurring particles in the northern Gulf of Aqaba (Red Sea). Marine Biology, 151(4), 1261-1274. DOI: https://doi.org/10.1007/s00227-006-0569-9
  » https://doi.org/10.1007/s00227-006-0569-9
• Falabella, V. (Ed.). 2017. Área Marina Protegida Namuncurá - Banco Burwood. Buenos Aires, Presidencia de la Nación.
• Fernández-Severini, M. D. & Hoffmeyer, M. S. 2005. Mesozooplankton assemblages in two bays in the Beagle Channel (Argentina) during January, 2001. Scientia Marina, 69(S2), 27-37. DOI: https://doi.org/10.3989/scimar.2005.69s227
  » https://doi.org/10.3989/scimar.2005.69s227
• Giesecke, R., Martín, J., Piñones, A., Höfer, J., Garcés-Vargas, J., Flores-Melo, X., Alarcón, E., Durrieu de Madron, X., Bourrin, F. & González, H. E. 2021. General Hydrography of the Beagle Channel, a Subantarctic Interoceanic Passage at the Southern Tip of South America. Frontiers in Marine Science, 8. DOI: https://doi.org/10.3389/fmars.2021.621822
  » https://doi.org/10.3389/fmars.2021.621822
• Gómez-Gómez, M., Danglot-Banck, C. & Vega-Franco, L. 2003. Sinopsis de pruebas estadísticas no paramétricas. Cuándo usarlas. Revista Mexicana de Pediatría, 70(2), 91-99.
• Gradinger, R., Friedrich, C. & Spindler, M. 1999. Abundance, biomass and composition of the sea ice biota of the Greenland Sea pack ice. Deep Sea Research Part II: Topical Studies in Oceanography, 46(6-7), 1457-1472. DOI: https://doi.org/10.1016/S0967-0645(99)00030-2
  » https://doi.org/10.1016/S0967-0645(99)00030-2
• Guichard, F. & Bourget, E. 1998. Topographic heterogeneity, hydrodynamics, and benthic community structure:a scale-dependent cascade. Marine Ecology Progress Series, 171, 59-70. DOI: https://doi.org/10.3354/meps171059
  » https://doi.org/10.3354/meps171059
• Guinder, V. A., Popovich, C. A., Molinero, J. C. & Perillo, G. M. E. 2010. Long-term changes in phytoplankton phenology and community structure in the Bahía Blanca Estuary, Argentina. Marine Biology, 157(12), 2703-2716. DOI: https://doi.org/10.1007/s00227-010-1530-5
  » https://doi.org/10.1007/s00227-010-1530-5
• Hamamé, M. & Antezana, T. 1999. Chlorophyll and zooplankton in microbasins along the Strait of Magellan - Beagle Channel passage. Scientia Marina, 63(S1), 35-42. DOI: https://doi.org/10.3989/scimar.1999.63s135
  » https://doi.org/10.3989/scimar.1999.63s135
• Hays, G. C., Richardson, A. J. & Robinson, C. 2005. Climate change and marine plankton. Trends in Ecology & Evolution, 20(6), 337-344. DOI: https://doi.org/10.1016/j.tree.2005.03.004
  » https://doi.org/10.1016/j.tree.2005.03.004
• Hlopec, R., Colombo, L., Curto, E. D., Loekemeyer, N., D´Annuncio, C. G. & Carranza, M. L. C. M. L. 2021. Reserva provincial Isla de los Estados, Isla de Año Nuevo e islotes adyacentes. La Lupa. Colección fueguina de divulgación científica, 11(18), 14-17.
• Hopcroft, R. R., Roff, J. C. & Chavez, F. P. 2001. Size paradigms in copepod communities: a re-examination. Hydrobiologia, 453(1), 133-141. DOI: https://doi.org/10.1023/A:1013167917679
  » https://doi.org/10.1023/A:1013167917679
• Iachetti, C. M., Lovrich, G. & Alder, V. A. 2021. Temporal variability of the physical and chemical environment, chlorophyll and diatom biomass in the euphotic zone of the Beagle Channel (Argentina): Evidence of nutrient limitation. Progress in Oceanography, 195, 102576. DOI: https://doi.org/10.1016/j.pocean.2021.102576
  » https://doi.org/10.1016/j.pocean.2021.102576
• Inkscape Project. 2024. Inkscape (Version Inkscape 1.4 (86a8ad7, 2024-10-11)). Available from: Available from: https://inkscape.org Access date: 2026 Apr. 27.
  » https://inkscape.org
• Irigoien, X., Chust, G., Fernandes, J. A., Albaina, A. & Zarauz, L. 2011. Factors determining the distribution and betadiversity of mesozooplankton species in shelf and coastal waters of the Bay of Biscay. Journal of Plankton Research, 33(8), 1182-1192. DOI: https://doi.org/10.1093/plankt/fbr026
  » https://doi.org/10.1093/plankt/fbr026
• Loeuille, N. & Loreau, M. 2005. Evolutionary emergence of size-structured food webs. Proceedings of the National Academy of Sciences, 102(16), 5761-5766. DOI: https://doi.org/10.1073/pnas.0408424102
  » https://doi.org/10.1073/pnas.0408424102
• Longhurst, A. R. 2010. Ecological geography of the sea Burlington, Elsevier.
• Margalef, R. 1973. Information theory in ecology Burlington, Fisheries Research Board of Canada.
• Massicotte, P. & South, A. 2023. rnaturalearth: World Map Data from Natural Earth (Version R package version 1.0.1). Available from: Available from: https://CRAN.R-project.org/package=rnaturalearth Access date: 2026 Apr. 27.
  » https://CRAN.R-project.org/package=rnaturalearth
• Matano, R. P., Palma, E. D. & Combes, V. 2019. The Burdwood Bank circulation. Journal of Geophysical Research: Oceans, 124(10), 6904-6926. DOI: https://doi.org/10.1029/2019JC015001
  » https://doi.org/10.1029/2019JC015001
• Mauchline, J. 1998. The biology of calanoid copepods. Advances in Marine Biology, v. 33, 710 p.
• NOAA PolarWatch. 2024. Chlorophyll from Aqua MODIS, NASA Polar Map Preview on PolarWatch Available from: Available from: https://modis.gsfc.nasa.gov/data/dataprod/chlor_a.php Access date: 2026 May 15.
  » https://modis.gsfc.nasa.gov/data/dataprod/chlor_a.php
• Oksanen, J., Simpson, G. L., Blanchet, F. G., Kindt, R., Legendre, P., Minchin, P. R., O’Hara, R. B., Solymos, P., Stevens, M. H. H., Szoecs, E., Wagner, H., Barbour, M., Bedward, M., Bolker, B., Borcard, D., Borman, T., Carvalho, G., Chirico, M., Caceres, M., Durand, S., Evangelista, H. B. A., FitzJohn, R., Friendly, M., Furneaux, B., Hannigan, G., Hill, M. O., Lahti, L., Martino, C., McGlinn, D., Ouellette, M.-H., Cunha, E. R., Smith, T., Stier, A., Braak, C. J. F. T. & Weedon, J. 2024. vegan: Community Ecology Package. Available from: Available from: https://CRAN.R-project.org/package=vegan Access date: 2026 Apr. 27.
  » https://CRAN.R-project.org/package=vegan
• Pielou, E. C. 1969. An introduction to mathematical ecology New York : Wiley-Interscience.
• Piola, A. R. & Rivas, A. L. 1997. Corrientes en la plataforma continental. In: Antecedentes históricos de las exploraciones en el mar y las características ambientales (Vol. 1, pp. 119-132). Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP): Mar del Plata. Available from: http://hdl.handle.net/1834/1704
  » http://hdl.handle.net/1834/1704
• Ponce, J. F. & Fernández, M. 2013. Climate. In: Climatic and Environmental History of Isla de los Estados, Argentina (pp. 13-23). Springer. DOI: https://doi.org/10.1007/978-94-007-4363-2
  » https://doi.org/10.1007/978-94-007-4363-2
• Presta, M. L., Capitanio, F. L. & Hoffmeyer, M. S. 2019. Spatio-temporal dynamics of mesozooplankton in the subantarctic Beagle Channel: The case of Ushuaia Bay (Argentina). Regional Studies in Marine Science, 28, 100546. DOI: https://doi.org/10.1016/j.rsma.2019.100546
  » https://doi.org/10.1016/j.rsma.2019.100546
• Presta, M. L., Hoffmeyer, M. S. & Capitanio, F. L. 2020. Mesozooplankton succession in a sub-Antarctic bay (Beagle channel, Southern tip of South America): distinctive annual patterns between two environmentally different zones. Polar Biology, 43(9), 1175-1191. DOI: https://doi.org/10.1007/s00300-020-02698-z
  » https://doi.org/10.1007/s00300-020-02698-z
• Presta, M. L., Riccialdelli, L., Bruno, D. O., Castro, L. R., Fioramonti, N. E., Florentín, O. V., Berghoff, C. F., Capitanio, F. L. & Lovrich, G. A. 2023. Mesozooplankton community structure and trophic relationships in an austral high-latitude ecosystem (Beagle Channel): the role of bottom-up and top-down forces during springtime. Journal of Marine Systems, 240, 103881. DOI: https://doi.org/10.1016/j.jmarsys.2023.103881
  » https://doi.org/https://doi.org/10.1016/j.jmarsys.2023.103881
• QGIS Development Team. 2024. QGIS Geographic Information system (Version 3.36.3-Maidenhead). QGIS Association. Available from: Available from: https://www.qgis.org Access date: 2026 Apr. 27.
  » https://www.qgis.org
• R Core Team. 2024. R: a language and environment for statistical computing. Available from: Available from: http://www.R-project.org/ Access date: 2026 Apr. 27.
  » http://www.R-project.org/
• Rakhesh, M., Raman, A. V. & Sudarsan, D. 2006. Discriminating zooplankton assemblages in neritic and oceanic waters: a case for the northeast coast of India, Bay of Bengal. Marine Environmental Research, 61(1), 93-109. DOI: https://doi.org/10.1016/j.marenvres.2005.06.002
  » https://doi.org/10.1016/j.marenvres.2005.06.002
• Riccialdelli, L., Becker, Y. A., Fioramonti, N. E., Torres, M., Bruno, D. O., Raya Rey, A. & Fernández, D. 2020. Trophic structure of southern marine ecosystems: a comparative isotopic analysis from the Beagle Channel to the oceanic Burdwood Bank area under a wasp-waist assumption. Marine Ecology Progress Series, 655, 1-27. DOI: https://doi.org/10.3354/meps13524
  » https://doi.org/10.3354/meps13524
• Sabatès, A., Gili, J. M. & Pagès, F. 1989. Relationship between zooplankton distribution, geographic characteristics and hydrographic patterns off the Catalan coast (Western Mediterranean). Marine Biology, 103(2), 153-159. DOI: https://doi.org/10.1007/BF00543342
  » https://doi.org/10.1007/BF00543342
• Sabatini, M. E. 2008. Life history trends of copepods Drepanopus forcipatus (Clausocalanidae) and Calanus australis (Calanidae) in the southern Patagonian shelf (SW Atlantic). Journal of Plankton Research, 30(9), 981-996. DOI: https://doi.org/10.1093/plankt/fbn062
  » https://doi.org/10.1093/plankt/fbn062
• Sabatini, M. E., Akselman, R., Reta, R., Negri, R. M., Lutz, V. A., Silva, R. I., Segura, V., Gil, M. N., Santinelli, N. H., Sastre, A. V., Daponte, M. C. & Antacli, J. C. 2012. Spring plankton communities in the southern Patagonian shelf: Hydrography, mesozooplankton patterns and trophic relationships. Journal of Marine Systems, 94, 33-51. DOI: https://doi.org/10.1016/j.jmarsys.2011.10.007
  » https://doi.org/10.1016/j.jmarsys.2011.10.007
• Sabatini, M. E., Giménez, J. & Rocco, V. 2001. Características del zooplancton del área costera de la plataforma patagónica austral (Argentina), Boletín. Instituto Español de Oceanografía, 17(3-4), 245-254.
• Sabatini, M. E., Ramírez, F. C. & Martos, P. 2000. Distribution pattern and population structure of Calanus australis Brodsky, 1959 over the southern Patagonian Shelf off Argentina in summer. ICES Journal of Marine Science, 57(6), 1856-1866. DOI: https://doi.org/10.1006/jmsc.2000.0969
  » https://doi.org/10.1006/jmsc.2000.0969
• Sabatini, M. E., Reta, R., Lutz, V. A., Segura, V. & Daponte, C. 2016. Influence of oceanographic features on the spatial and seasonal patterns of mesozooplankton in the southern Patagonian shelf (Argentina, SW Atlantic). Journal of Marine Systems, 157, 20-38. DOI: https://doi.org/10.1016/j.jmarsys.2015.12.006
  » https://doi.org/10.1016/j.jmarsys.2015.12.006
• Schlitzer & Reiner. 2023. Ocean Data View. Available from: https://odv.awi.de/
  » https://odv.awi.de/
• Shannon, C. E. 1948. A mathematical theory of communication. The Bell System Technical Journal, 27(3), 379-423. DOI: https://doi.org/10.1002/j.1538-7305.1948.tb01338.x
  » https://doi.org/10.1002/j.1538-7305.1948.tb01338.x
• Skjoldal, H.-R., Wiebe, P. H. & Foote, K. G. 2000. 2 - Sampling and experimental design. In Harris, R., Wiebe, P., Lenz, J., Skjoldal, H. R., & Huntley, M. (Ed.). ICES Zooplankton Methodology Manual (pp. 33-53). London: Academic Press.
• South, A., Schramm, M. & Massicotte, P. 2024a. rnaturalearthdata: world vector map data from natural earth used in ‘rnaturalearth’ (Version R package version 1.0.0). Available from: Available from: https://CRAN.R-project.org/package=rnaturalearthdata Access date: 2026 Apr. 27.
  » https://CRAN.R-project.org/package=rnaturalearthdata
• South, A., Schramm, M. & Massicotte, P. 2024b. rnaturalearthhires: high resolution world vector map data from natural earth used in rnaturalearth (Version R package version 1.0.0.9000). Available from: Available from: https://github.com/ropensci/rnaturalearthhires Access date: 2026 Apr. 27.
  » https://github.com/ropensci/rnaturalearthhires
• Spinelli, M. L., Malits, A., García Alonso, V. A., Martín, J. & Capitanio, F. L. 2020. Spatial gradients of spring zooplankton assemblages at the open ocean sub-Antarctic Namuncurá Marine Protected Area/Burdwood Bank, SW Atlantic Ocean. Journal of Marine Systems, 210, 103398. DOI: https://doi.org/10.1016/j.jmarsys.2020.103398
  » https://doi.org/10.1016/j.jmarsys.2020.103398
• Stemmann, L. & Boss, E. 2012. Plankton and particle size and packaging: from determining optical properties to driving the biological pump. Annual Review of Marine Science, 4, 263-290. DOI: https://doi.org/10.1146/annurev-marine-120710-100853
  » https://doi.org/10.1146/annurev-marine-120710-100853
• Taylor, A. H., Allen, J. I. & Clark, P. A.2002. Extraction of a weak climatic signal by an ecosystem, Nature, 416, 629-632. DOI: https://doi.org/10.1038/416629a
  » https://doi.org/10.1038/416629a
• Tombesi, M. L., Rabuffettio, F. & Lovrich, G. A. 2020. Las áreas marinas protegidas en la Argentina. La Lupa. Colección fueguina de divulgación científica, (16), 2-7.
• Turner, J. 2004. The importance of small planktonic copepods and their roles in pelagic marine food webs. Zoological Studies, 43(2), 255-266.
• Vargas, M., Brown, C. W. & Sapiano, M. R. P. 2009. Phenology of marine phytoplankton from satellite ocean color measurements. Geophysical Research Letters, 36(1). DOI: https://doi.org/10.1029/2008GL036006
  » https://doi.org/10.1029/2008GL036006
• Verity, P. G. & Smetacek, V. 1996. Organism life cycles, predation, and the structure of marine pelagic ecosystems. Marine Ecology Progress Series, 130(1-3), 277-293.
• Warwick, R. M. & Gee, J. M. 1984. Community structure of estuarine meiobenthos. Marine Ecology Progress Series, 18, 97-111. DOI: https://doi,org/10.3354/meps018097
  » https://doi.org/10.3354/meps018097

• AI Use statement:
  Artificial intelligence tools (ChatGPT) were used exclusively to refine the English language of this manuscript. The content was carefully reviewed by the authors to ensure consistency and correctness, and the authors are fully responsible for the final version of the manuscript.
• Funding:
  The scientific missions were financed by the Argentine National State through funds provided under the law establishing the Namuncurá/Burdwood Bank Marine Protected Area. This study was supported by the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina (PIP 11220150100109CO), the Universidad de Buenos Aires, Argentina (UBACYT 20020190100133BA, 2020-2024), ANPCyT (PICT-2019-04049), and the Pampa Azul Interministerial Initiative implemented by the Argentine Ministry of Science, Technology and Productive Innovation. The authors sincerely thank the reviewers for their valuable comments and suggestions, which contributed to improving this manuscript. This is contribution 104 of the Namuncurá/Burdwood Bank Marine Protected Area (Law 26,875).

Edited by

• Associate Editor:
  Petra Lenz

Publication Dates

• Publication in this collection
  03 Aug 2026
• Date of issue
  2026

History

• Received
  17 Dec 2025
• Accepted
  17 Apr 2026