Mesozooplankton Community Structure Research Articles

Environmental drivers of mesozooplankton dynamics in the Munroe Island, adjacent to Ashtamudi Estuary, India.

The response of mesozooplankton is critical in assessing the health of an estuarine ecosystem. Reports on the spatial and temporal dynamics of mesozooplankton community in estuarine and backwaters of the Southern parts of India are scanty. In this scenario, we appraised the community structure of mesozooplankton and their spatio-temporal dynamics based on various multivariate statistical assessments. A total of 31 taxa were identified and the abundance was principally dominated by Copepoda followed by Luciferidae during three sampling seasons. The most abundant species were: Paracalanus parvus parvus, Pseudodiaptomus aurivillii, Temora stylifera, and Pseudodiaptomus serricaudatus. Canonical correspondence analysis and Spearman's correlation coefficients underlined that salinity, turbidity, conductivity, temperature, dissolved oxygen, chlorophyll a (Chl-a), and nutrients were the principal environmental variables strongly linked with mesozooplankton dynamics in Munroe Island. The highest abundance of mesozooplankton was recorded in MoN (monsoon), followed by PrM (pre-monsoon), and PoM (post-monsoon). Hierarchical clustering confirmed that the grouping of sampling stations is based on the estuarine and freshwater influences on mesozooplankton abundance. During the entire investigation, various ecological indices were observed in good condition. Moreover, the optimum environmental conditions during the PoM season are marked with the highest indices values. Overall, multivariate investigations undoubtedly proved the suitability of mesozooplankton communities as potential bioindicators for spatial and seasonal ecological assessments. Our investigation emphasizes the high assemblages of mesozooplankton and their responses to various environmental variables and highlights the significance of long-term ecological monitoring in a threatened ecosystem like Munroe Island.

Spatial Distribution Pattern of the Mesozooplankton Community in Ross Sea Region Marine Protected Area (RSR MPA) during Summer

The Ross Sea region Marine Protected Area (RSR MPA) is one of the most productive regions in the Southern Ocean. Mesozooplankton intermediates the primary product to the higher predators, such as penguins and seals, in this ecosystem. In this study, the mesozooplankton community structure and spatial pattern in the RSR MPA in January were investigated by using 505 μm-mesh-size bongo net samples. As a result, 37 mesozooplankton taxa with a total mean abundance of 35.26 ind./m3, ranging from 2.94 to 139.17 ind./m3, were confirmed. Of the 37 taxa, 7 occupied almost 84% of the total abundance, with copepods being the main dominant taxa. As shown by our hierarchical analysis, the mesozooplankton community was divided into four groups, each associated with a specific geographical distribution. Group A was composed of stations around Terra Nova Bay and showed relatively low abundance. Group B included stations around the continental slope region. Group D was composed of the Ross Sea continental shelf stations, while group C consisted of stations geographically located between those of groups B and D. These four groups were influenced by various environmental factors, such as water temperature, salinity, and nutrients. In summary, the mesozooplankton community can be separated according to geographical pattern. This pattern is related to several environmental factors.

Seasonal variation in the mesozooplankton community structure and indicator species of the Yellow Sea

We investigated the mesozooplankton community structure of the Yellow Sea in four seasons, one season for each year during 2019–2022. Total abundance and biomass were highest in autumn and spring, respectively. The mesozooplankton community was dominated by small copepods such as Acartia, Paracalanus, and Oithona species throughout all seasons. Euphausiid larvae were particularly abundant in spring, whereas tunicates appeared only in autumn. In spring, summer, and winter, mesozooplankton were clustered into groups from coastal waters to the open ocean. However, in autumn, the mesozooplankton community was divided by latitude and indicator species analysis suggested the influence of a warm current in this season. A comparison of our findings with those of previous studies indicated no clear change in zooplankton species composition or its seasonality in the Yellow Sea within the past 30 years.

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

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

Identification of tipping years and shifts in mesozooplankton community structure using multivariate analyses: a long-term study in southern North Sea

Abstract Many previous studies on the changes in zooplankton communities considered only subsets of the total community. In this study, we investigated the temporal dynamics of the mesozooplankton community structure, considering all taxa (holo- and meroplankton) sampled over the last five decades at Helgoland Roads. We identified two tipping years. The first one occurred in 1983, which is consistent with previous studies conducted on copepods. The second shift, even more pronounced, took place in the mid-2000s. During the first shift, most taxa significantly increased in abundance and kept high densities until the end of the 1990s. Then, we observed in the mid-2000s a sharp decrease in community diversity and abundances of almost all taxa. One of the aims of the study was to test the robustness depending on the choice of taxa. To test this, we selected different subsets of the total zooplankton community, both randomly as well as based on functionality. We observed very similar trends over time for all groups, showing the complete community experienced the same changes. However, the timing of the tipping years depended on the organisms considered. These results highlight that the observed changes in the planktonic community are surprisingly robust and visible in most planktonic organisms.

Summer distribution and community structure of surface water mesozooplankton from the eastern Mediterranean Sea

The zooplankton community structure and its relationship with environmental parameters were evaluated in the surface waters (0–50 m) of the eastern Mediterranean (the Aegean Sea’s coastal waters and the Levanine Sea’s coastal and offshore waters), from coastal waters to open sea waters, during the summer for two years. A total of 157 species/groups were registered in the study area. Copepods, cladocerans, doliolids, meroplankton and appendicularians represented the most important zooplankton groups. Five copepod species (Corycaeus [Onychocorycaeus] ovalis, Goniopsyllus clausi, Oncaea scottodicarloi, Sapphirina bicuspidata and Scaphocalanus curtus) have been recorded for the first time in Turkish coastal regions; three species (Centropages bradyi, Goniopsyllus clausi and Oncaea scottodicarloi) had not previously been found in the Aegean Sea; and one species (Goniopsyllus clausi) has been added for the first time to the eastern Mediterranean fauna. Moreover, Pleopis schmackeri was already found to be present in both the Aegean Sea and Mediterranean coasts of Turkey in August 2006. Dominant species varied from the coastal waters to open waters. A small number of species belonging to the coastal community (e.g. Penilia avirostris, Pseudevadne tergestina, Oithona plumifera, Paracalanus parvus and Centropages kroyeri) dominated all coastal areas. In contrast, the open water stations were characterised by the presence of typically epipelagic species of the Mediterranean Sea (e.g. Calocalanus spp., Clausocalanus furcatus, Lucicutia flavicornis, Mecynocera clausi, Farranula rostrata, Oncaea scottodicarloi and Oncaea mediterranea).

Impacts of hypoxia on the mesozooplankton community structure in a semi-enclosed bay

Gamak Bay is frequently affected by hypoxia in summer. Therefore, this study aimed to examine the effect of hypoxia on the mesozooplankton community of this region. Mesozooplankton samples were obtained biweekly (28 times) at a hypoxic station (inner bay) and a normoxic station (middle bay) using a conical net (mesh size 200 μm; mouth diameter 30 cm) from April 2020 to April 2021. In the inner bay, hypoxia was observed a total of five times between early June and late September, whereas no instances of hypoxia were detected in the middle bay. During the hypoxic period, mesozooplankton abundance was higher in the inner bay than the middle bay (p < 0.05). During the normoxic period, there was no difference between the inner bay and the middle bay (p > 0.05). The dominant species in the hypoxic period were three species of cladocerans (Pleopis polyphemoides, Pseudoevadne tergestina, Penilia avirostris) and the copepod Acartia sinjiensis. The abundance of cladocerans was higher in the inner bay, and that of A. sinjiensis was higher in the middle bay (p < 0.05). In addition to water temperature, salinity, and size-fractionated Chl-a concentration, mesozooplankton abundance was also significantly correlated with the bottom DO concentration. Collectively, our findings suggest that hypoxia can affect mesozooplankton abundance and occurrence times.

Seasonal mesozooplankton patterns and timing of life history events in high-arctic fjord environments

Seasonal patterns in mesozooplankton composition, vertical distribution, and timing of reproduction are challenging to study in the open sea due to ocean currents and mix of populations of different origins. Sill fjords, on the other hand, with restricted water exchange, are ideal locations for studying taxa- and community-specific adaptations to the prevailing environment. Here, we present re-occurring patterns in the mesozooplankton community structure in Billefjorden, Svalbard, a high Arctic sill fjord with extensive seasonal ice cover, based on monthly sampling from 2011 to 2013. The zooplankton community composition confirmed the Arctic character of this fjord. Predominantly herbivorous taxa, such as Calanus glacialis and Pseudocalanus spp., showed strong seasonal variation in abundance and depth distribution, with population minima in spring being compensated by a rapid population recovery during summer. Omnivorous taxa, such as Microcalanus spp. and copepods of the family Aetideidae, largely remained at depth throughout the year and had an extended or year-round reproductive period. Deep-dwelling omnivorous/carnivorous species peaked in abundance in winter–spring when herbivorous populations were severely depleted. Taxa with seasonally limited occurrences, i.e., meroplankton, peaked in spring and summer at the surface, but were largely absent for the rest of the year. The different life histories, with contrasting feeding modes, depth preferences, and timing of reproduction lead to reduced interspecies competition and allow for a rather high and stable abundance of mesozooplankton year-round despite the short primary production window at high latitudes.

Multi-storm analysis reveals distinct zooplankton communities following freshening of the Gulf of Mexico shelf by Hurricane Harvey

Tropical cyclones can highly modify coastal ecosystems through interactions between their unique set of meteorological traits and an ecosystem’s antecedent conditions. As such, resultant changes to biological community structure are likely storm-specific, yet our understanding of cyclone effects on marine communities is limited compared to communities in terrestrial and freshwater habitats. Using northwestern Gulf of Mexico (NWGOM) mesozooplankton data, we tested: (1) for differences between storm and non-storm community structure and dispersion; (2) if post-storm communities varied between one another; (3) if salinity drove differences; and (4) if physical drivers of abundance and evenness varied between storm and non-storm communities. Mesozooplankton community structure following Hurricanes Harvey, Ike, Rita, and during five non-storm years were analyzed. Post-Ike, post-Rita, and non-storm communities were similar while post-Harvey communities were distinct from non-storm years. A structural equation model revealed stratification and abundance drove community evenness. Post-Harvey mesozooplankton were more abundant in low salinity waters; a pattern muted during non-storm years. NWGOM mesozooplankton community structure was generally resilient to hurricane effects, except when large changes in salinity occurred. Our findings suggest resource availability for planktivorous predators and energy transfer within coastal food webs is altered following cyclones with high precipitation rates.

Effects of Terrestrial Inputs on Mesozooplankton Community Structure in Bohai Bay, China

Zooplankton play a pivotal role in connecting primary producers and high trophic levels, and changes in their temporal and spatial distribution may affect the entire marine ecosystem. The spatial and seasonal taxonomic composition patterns of mesozooplankton in Bohai Bay were investigated in relation to a number of water parameters. Bohai Bay is a eutrophic semi-enclosed bay with dynamic physico-chemical conditions influenced by terrestrial inputs and seawater intrusion. The results showed that under the condition of terrigenous input, the diversity of mesozooplankton species near the eutrophic Haihe River Estuary and Jiyun River Estuary was lower than that in the central Bohai Bay, with gelatinous Oikopleura dioica as the dominant species. The mesozooplankton diversity was highest in the bay mouth affected by seawater intrusion, and the dominant oceanic species, mainly copepods Corycaeus affinis, Calanus sinicus, and Oithona similis, entered the inner bay from the bay mouth. Meanwhile, the abundance of mesozooplankton in summer was significantly higher than that in autumn. Compared with historical data, the dominant species in Bohai Bay has evolved from arrow worm Sagitta crassa to copepod Paracalanus parvus, probably due to global warming, indicating the effects of human activities on the succession of mesozooplankton community.

Effects of environmental variables on mesozooplankton dynamics in an Amazonian estuary

In the present study, it was analyzed the structure of mesozooplankton community, and their spatio-temporal variations along the Caeté River estuary (northeast of Pará, Brazil). Samples were collected during spring tides conducted in nychthemeral cycles, in three fixed sectors located along the studied estuary (inner-S1, middle-S2 and outer-S3), using conical plankton nets of 200 μm mesh size. Samplings were performed in September 2014 (dry season) and March 2015 (rainy season), totaling 54 samples. A total of 25 mesozooplankton species were recorded, being the copepods the most diversified group (21 species), mostly dominated by estuarine and coastal species. The most abundant mesozooplankton species presented significantly higher densities ( p <0.0001) between the middle ( Pseudodiaptomus richardi , 583.8±956.5 ind m −3 , Paracalanus quasimodo, 108.9±181.4 ind m −3 and Pseudodiaptomus acutus, 23.4±66.6 ind m −3 ) and outer ( Acartia tonsa, 476.9±1,298.8 ind m −3 and Acartia lilljeborgii (407.9±1,038.1 ind m −3 and Parasagitta tenuis , 59.9±117.1 ind m −3 ) sectors. The non-metric multidimensional ordination analysis highlighted that the average density of the main species varied mainly at a spatial scale, with density increasing toward the mouth of the estuary (except for P. richardi ). Spearman's correlation ( rs ) demonstrated that the salinity, turbidity, dissolved nutrients and chlorophyll a concentrations were the prevailing environmental variables associated with significant spatial changes of mesozooplankton distribution in this area. Overall, the results showed that spatial variation in the water physicochemical characteristics of the Caeté Estuary have significant effects on the structure and succession of the mesozooplankton, which may potentially affect the functioning and biodiversity of this coastal ecosystem.

Distribution of the Mesozooplankton Community in the Western Ross Sea Region Marine Protected Area During Late Summer Bloom

The spatio-temporal distributions of the epipelagic mesozooplankton community in the western Ross Sea region marine protected area (RSR MPA) were investigated. Mesozooplankton surveys were conducted in February 2018, January 2019, and March 2020 from an approximate depth of 200 m to address the essential environmental factors influencing the mesozooplankton community structure. Our results showed that the mesozooplankton community of the western RSR MPA could be affected by the various ecological factors, depending on their temporal and spatial variations. The community structure in 2018 was distinguished by its chlorophyll-a (Chl-a) concentration during the summer bloom phase in the late summer. Taxa observed in 2019 were divided into four significantly different groups according to the body size of the community composition. This differentiation could be derived from predation pressure, inducing a trophic cascade. Taxa in the 2020 samples were separated into five different groups based on temperature; during the 2020 survey, the water temperature was low and sea ice covered the whole continental shelf in the Ross Sea. Additionally, comparing the results from the three interannual surveys, although the communities clustered according to the survey period, the continental shelf groups were quite dissimilar despite overlapping geographically. Taken all together, the mesozooplankton community of the western RSR MPA changed according to changes in several ecological factors, such as temperature, Chl-a concentration, and predation pressure. The occurrence of summer blooms and the decline in water temperature mainly regulated the mesozooplankton community structure in the late summer.

Corrigendum: Investigating Seasonal Succession Patterns in Mesozooplankton Community Structure Following Hurricane Harvey

Corrigendum: Investigating Seasonal Succession Patterns in Mesozooplankton Community Structure Following Hurricane Harvey

Basin-scale distribution of salps and doliolids in the transition region of the North Pacific Ocean in summer: Drivers of bloom occurrence and effect on the pelagic ecosystem

The large-scale distribution of thaliaceans in relation to environmental variables was investigated over 4500 km in the transition region of the North Pacific (36°N–43.6° N, 141.5° E–164.5° W) in the summer of 2016–2019. Three main patterns occurred in the thaliacean bloom formations with specific and annual variabilities. Thalia democratica, the most dominant thaliacean species in this region, formed an intensive bloom (>100 ind m−3) of up to 300 km, mainly south of the subarctic boundary between 160° E and 180°. The bloom was accompanied by a dense water mass which was associated with high nutrient concentration and N/P ratio, indicating that this species thrived under the influence of the HNLC water mass from the subarctic region. A Dolioletta gegenbauri bloom was observed east of 180° and the north of the subarctic boundary in association with higher chlorophyll a levels. Doliolum denticulatum and Doliolum nationalis increased with sea surface temperature and pico-sized chlorophyll a, suggesting adaptation to oligotrophic subtropical waters. Estimated grazing and downward flux by Thalia democratica bloom corresponded to 63–80% and 20–26% of daily primary production, respectively, indicating that the bloom enhanced the biological pump in the HNLC-like environment dominated by small phytoplankton. Doliolids function as important components of the microbial food web through the consumption of varied organic matter. Thaliaceans utilise the specific niche which suspension-feeding copepods find difficult to colonise, indicating that bottom-up control of oceanographic conditions determines the mesozooplankton community and food-web structure in the transition region.

Seasonal Variability in the Zooplankton Community Structure in a Sub-Arctic Fjord as Revealed by Morphological and Molecular Approaches

Phyto- and zooplankton in Arctic and sub-Arctic seas show very strong seasonal changes in diversity and biomass. Here we document the seasonal variability in the mesozooplankton community structure in a sub-Arctic fjord in Northern Norway based on monthly sampling between November 2018 and February 2020. We combined traditional morphological zooplankton identification with DNA metabarcoding of a 313 base pair fragment of the COI gene. This approach allowed us to provide the most detailed mesozooplankton species list known for this region across an entire year, including both holo- and meroplankton. The zooplankton community was dominated by small copepods throughout the sampling period both in terms of abundance and relative sequence counts. However, meroplankton was the most diverse group, especially within the phylum polychaeta. We identified four distinct periods based on the seasonal analysis of the zooplankton community composition. The pre-spring bloom period (February–March) was characterized by low abundance and biomass of zooplankton. The spring bloom (April) was characterized by the presence of Calanus young stages, cirripedia and krill eggs. The spring-summer period (May–August) was characterized by a succession of meroplankton and a relatively high abundance of copepods of the genus Calanus spp. Finally, the autumn-winter period (September–December) was characterized by a high copepod diversity and a peak in abundance of small copepods (e.g., Oithona similis, Acartia longiremis, Pseudocalanus acuspes, Pseudocalanus elongatus, Pseudocalanus moultoni, Pseudocalanus minutus). During this period, we also observed an influx of boreal warm-water species which were notably absent during the rest of the year. Both the traditional community analysis and metabarcoding were highly complementary and with a few exceptions showed similar trends in the seasonal changes of the zooplankton community structure.

Oceanographic structure and seasonal variation contribute to high heterogeneity in mesozooplankton over small spatial scales

Abstract The coastal oceans can be highly variable, especially near ocean fronts. The Ushant Front is the dominant oceanographic feature in the Iroise Sea (NE Atlantic) during summer, separating warm stratified offshore waters from cool vertically-mixed nearshore waters. Mesozooplankton community structure was investigated over an annual cycle to examine relationships with oceanographic conditions. DNA metabarcoding of COI and 18S genes was used in communities from six sites along two cross-shelf transects. Taxonomic assignments of 380 and 296 OTUs (COI and 18S, respectively) identified 21 classes across 13 phyla. Meroplankton relative abundances peaked in spring and summer, particularly for polychaete and decapod larvae, respectively, corresponding to the reproductive periods of these taxa. Meroplankton was most affected by season, while holoplankton varied most by shelf position. Copepods with a mixed feeding strategy were associated with the most offshore sites, especially in the presence of the front, while filter-feeding or carnivorous copepods were associated with nearshore sites. In sum, mesozooplankton communities in well-mixed coastal waters were distinct from those found in the Ushant Front (high thermal stratification and chlorophyll-a). Furthermore, the benthic compartment, through its partial life cycle in the water column, contributed to high heterogeneity in planktonic communities over short temporal and spatial scales.

Hydrodynamic variability and nutrient status structuring the mesozooplankton community of the estuaries along the west coast of India.

The influence of distinct tidal characteristics and nutrient status on mesozooplankton community was studied in six major estuaries along the west coast of India during the late-monsoon (MS) and post-monsoon (PM) periods. The macro-tidal estuaries in the north (Amba and Thane) exhibited higher nutrient concentration compared to the micro- and meso-tidal estuaries located in the south (Cochin and Nethravati) and central (Zuari and Mandovi) west coast of India. The markedly higher nitrate and phosphate levels in the macro-tidal estuaries during PM indicated anthropogenic contributions from domestic and industrial effluents, which significantly impacted the mesozooplankton community structure. Nutrient enrichments favored higher phytoplankton standing stock leading to low DO levels. In the micro- and meso-tidal estuaries, meso- and euryhaline copepods dominated whereas in the macro-tidal estuaries, the copepod community was dominated by euryhaline and coastal species. Furthermore, the high-saline eutrophic environment of macro-tidal estuaries formed congenial for the increased jellyfish preponderance during PM. The predation pressure exerted by the jellyfish population on the crustacean zooplankton and ichthyoplankton exerted an adverse impact on the potential fishery stock in the macro-tidal estuaries. Thus, the study reveals that the nutrient enrichment favoring a shift in the mesozooplankton community structure from nutritionally superior crustacean plankton to less desirable jellyfishes, which in turn, may lead to a threat on the estuarine pelagic energy transfer and ecosystem deliverables.

Spatio-temporal drivers of microphytoplankton community in the Bay of Biscay: Do species ecological niches matter?

From 2000 to 2016, substantial changes in biomass and community structure of small pelagic fish and mesozooplankton have been reported in the Bay of Biscay. Since significant relationships have been found between phytoplankton chlorophyll a and mesozooplankton as well as between phytoplankton chlorophyll a and shifts in sardine body condition, it was hypothesized that phytoplankton communities may have also been affected during this period and may have played a role in these changes. However, the available data were insufficient to validate this hypothesis and the causes of these changes remained unexplained. The present study analyzed a spatio-temporal marine microphytoplankton dataset collected during the annual PELGAS (PELagiques GAScogne) surveys from 2003 to 2014. The thorough analysis of microphytoplankton taxonomic composition, with an approach integrating the relative role of environmental conditions as well as biotic interactions and applying the concept of ecological niche, confirmed that significant modifications in microphytoplankton community structure occurred during this period. Temporal changes were stronger than spatial differences at these sampling scales. Three main periods, 2003–2005, 2006 and 2007–2014, showing different community structure, diversity and dominant taxonomic units were highlighted. Twenty eight taxonomic units were involved in these community changes. Among them, five were identified as the protagonists (Pseudo-nitzschia spp., Gymnodinium spp. + Gyrodinium spp., Leptocylindrus danicus, Leptocylindrus minimus and Chaetoceros sp.). Variations in water temperature and equivalent freshwater depth constrained the realized ecological niches of these species and explained, at least in part, changes in community structure. This study stresses the need to improve our knowledge of phytoplankton species ecological niches and to take into account biotic interactions for a thorough understanding of the processes shaping plankton communities and the resulting diversity patterns.

Extreme Levels of Ocean Acidification Restructure the Plankton Community and Biogeochemistry of a Temperate Coastal Ecosystem: A Mesocosm Study

The oceans’ uptake of anthropogenic carbon dioxide (CO2) decreases seawater pH and alters the inorganic carbon speciation – summarized in the term ocean acidification (OA). Already today, coastal regions experience episodic pH events during which surface layer pH drops below values projected for the surface ocean at the end of the century. Future OA is expected to further enhance the intensity of these coastal extreme pH events. To evaluate the influence of such episodic OA events in coastal regions, we deployed eight pelagic mesocosms for 53 days in Raunefjord, Norway, and enclosed 56–61 m3 of local seawater containing a natural plankton community under nutrient limited post-bloom conditions. Four mesocosms were enriched with CO2 to simulate extreme pCO2 levels of 1978 – 2069 μatm while the other four served as untreated controls. Here, we present results from multivariate analyses on OA-induced changes in the phyto-, micro-, and mesozooplankton community structure. Pronounced differences in the plankton community emerged early in the experiment, and were amplified by enhanced top-down control throughout the study period. The plankton groups responding most profoundly to high CO2 conditions were cyanobacteria (negative), chlorophyceae (negative), auto- and heterotrophic microzooplankton (negative), and a variety of mesozooplanktonic taxa, including copepoda (mixed), appendicularia (positive), hydrozoa (positive), fish larvae (positive), and gastropoda (negative). The restructuring of the community coincided with significant changes in the concentration and elemental stoichiometry of particulate organic matter. Results imply that extreme CO2 events can lead to a substantial reorganization of the planktonic food web, affecting multiple trophic levels from phytoplankton to primary and secondary consumers.

Mesozooplankton Community Structure in the Yellow Sea in Spring

Mesozooplankton Community Structure in the Yellow Sea in Spring