Abstract Coastal ecosystems play a major role in global carbon cycling and storage, yet the contribution of calcifying macroalgal habitats, such as coralline algal beds (CABs; rhodolith and maerl beds), remains poorly understood. Because carbon cycling in CABs is governed by community productivity and calcification, which exert opposing effects on seawater carbonate chemistry, understanding the balance between these processes is essential for determining whether CABs function as net carbon sinks or sources. Yet, community‐level measurements remain scarce, and the environmental and biological drivers of CAB carbon balance are largely unknown. Here, we quantified net community productivity (NCP), net community calcification (NCC), and the resulting net carbon balance (NCP : NCC) in shallow warm‐temperate and subtropical Atlantic CABs with contrasting rhodolith‐associated communities, using in situ benthic chamber incubations. All CABs were net autotrophic, with NCP : NCC ratios ≥ 0.6, indicating that they acted as potentially carbon neutral and net carbon sinks. By combining our measurements with available community‐level datasets, we identified light availability as the primary environmental driver of community productivity and calcification, whereas benthic community structure influenced the balance between these processes. Together, our findings demonstrate that CAB carbon balance is governed by the interaction between environmental conditions and community structure, providing the first mechanistic insight into the drivers of ecosystem carbon balance. This pronounced context dependency highlights the need for community‐level assessments across broader environmental and biological settings to test the generality of these relationships and determine under which conditions carbon burial in CABs translates into a net contribution to coastal carbon storage.
Abstract Phytoplankton blooms structure primary production and food‐web dynamics in the Gulf of Alaska, yet their response to recent warming and marine heatwaves (MHWs) remains poorly described. Using a parametric Gaussian framework applied to 21 years of satellite chlorophyll a (Chl a ), this study classified daily Chl a timeseries into double‐bloom, single spring‐bloom, single fall‐bloom, and no‐bloom regimes and related these to large‐scale oceanographic and atmospheric forcing. Double blooms with distinct spring and fall peaks dominated much of the domain in cold, dynamically active years characterized by negative sea surface temperature anomalies, depressed sea level, strong cross‐shelf pressure gradients, and more frequent storms associated with an intensified Aleutian Low. In contrast, warm years with elevated sea level and weaker cross‐shelf and atmospheric forcing favored single spring blooms and, in some areas, no‐bloom conditions, while single fall blooms occurred under intermediate physical states. Although no significant linear trends in the areal extent occupied by each regime were detected over 2003–2023, years influenced by major MHWs projected strongly onto the warm, weakly forced end of this physical gradient and were associated with reduced double‐bloom extent and an increased prevalence of single spring and no‐bloom regimes. These shifts imply that contraction and weakening of the seasonal production window, with likely consequences for zooplankton growth, match–mismatch dynamics for fish early life stages, and the balance between pelagic retention and export, highlighting how MHWs and ongoing climate change can suppress and reorganize phytoplankton bloom phenology in the Gulf of Alaska.
Abstract Warming and enhanced nutrient and organic matter (OM) pollution are pervasive drivers of global environmental change that may significantly influence the dynamics of coastal sediment phosphorus (P). Traditional studies have predominantly focused on individual environmental stressors. However, the superposition of multiple stressors can trigger additive or synergistic effects, thereby inducing a cascading response of P dynamics and potentially exacerbating the risk of ecosystem collapse. To elucidate the individual and combined impacts of multiple stressors on sediment P dynamics, we performed a 2‐month mesocosm experiment with factorial combinations of three temperature gradients and two sediment types differing in OM content under high nitrogen loading conditions. We found that: (i) warming and OM, each taken individually, increased sediment P release by 39–207% and 45%, respectively, whereas their combined effect collectively amplified P release to 179–440%; (ii) the interactive impacts of these two co‐occurring stressors on sediment P release were synergistic; (iii) these factors, along with their synergistic interactions, had a cascading net facilitation effect on P release; involving increased populations of phosphate‐solubilizing bacteria, up‐regulation of functional genes ( pho D), enhanced alkaline phosphatase activity, and decreased dissolved oxygen concentration. Combined, these factors, as suggested by piecewise structural equation modeling, explain up to 97% of the observed P release. Our findings provide novel insights into the interactive impacts of co‐occurring anthropogenic stressors on coastal P dynamics, highlighting the necessity of considering the synergistic effects of warming and OM pollution on P release in future conservation planning and coastal zone management.
Abstract Microzooplankton and mixoplankton are key regulators of marine food webs, yet their responses to ocean warming and thermal extremes remain incompletely integrated across physiological, community, and ecosystem scales. This synthesis examines how temperature shapes the physiology, trophic strategies, and community dynamics of these protistan functional groups using experimental, observational, and modeling evidence from marine systems and relevant contrasts from freshwater and saline inland waters. Short‐term experiments with heterotrophic microzooplankton show strong temperature dependence of growth and grazing, but increased respiratory demand can reduce gross growth efficiency, accelerating nutrient recycling without necessarily increasing biomass transfer to higher trophic levels. Mixoplankton deviate from strict heterotrophic expectations because warming can alter the balance between phototrophy and phagotrophy, rather than uniformly accelerating all rates. At the community level, warming can tighten grazer–prey coupling in productive systems, whereas warm, stratified, nutrient‐poor systems more often favor communities dominated by smaller prey, trophic flexibility, and recycling‐dominated pathways. Thermal variability, including marine heatwaves, introduces additional nonlinearities, temporal mismatches, and legacy effects that remain poorly represented in ecosystem models.
Abstract Despite increasing research on warming and biodiversity, knowledge on how temperature shapes community size structure remains limited, which is one of the main challenges in assessing the consequences of climate change. This gap is evident in vulnerable ecosystems like ponds, crucial for aquatic biodiversity but highly sensitive to temperature increases due to their small size. This study assessed the main climatic and local drivers influencing zooplankton community size structure in 141 ponds across four European countries and Uruguay, covering a wide latitudinal and trophic gradient with standardized sampling. Using linear mixed models, results revealed that local factors, such as trophic status and morphometric pond characteristics, were more consistently associated with size‐spectrum parameters than climatic variables. The normalized size spectrum slopes (ordinary least square regression, OLS) became steeper with higher chlorophyll a (Chl a ) concentrations, reflecting dominance of small zooplankton, suggesting reduced energy transfer efficiency to higher trophic levels, and possibly weaker top‐down phytoplankton control. Conversely, ponds with lower Chl a showed flatter slopes, indicating more large zooplankton and possibly greater top‐down control. The overall intercept was higher in deeper ponds with abundant aquatic vegetation, suggesting greater overall abundance across size classes. Size spectrum metrics did not vary significantly along climatic gradients. These results suggest that zooplankton community size structure in ponds appears to be more closely related to local environmental conditions than large‐scale climatic gradients. This highlights the key role of local habitat characteristics in shaping zooplankton size structure and energy transfer dynamics.
Abstract Gelatinous zooplankton are abundant in marine ecosystems, yet their trophic roles and functional diversity in food webs have only recently gained attention. Gelatinous zooplankton taxa including hydromedusae, ctenophores, siphonophores, chaetognaths, and pelagic tunicates span multiple phyla and are often grouped taxonomically, but trait‐based categorizations have emerged as an ecologically meaningful alternative. Considering their wide variety of diets and feeding modes, we examined whether gelatinous zooplankton diet diversity can be described by feeding mode or phylum categorizations. We analyzed the carbon and nitrogen stable isotope composition (δ 13 C and δ 15 N values) of 490 gelatinous zooplankton samples of 32 genera/species collected across seasons and shelf positions in the northern California Current ecosystem. The δ 13 C and δ 15 N values fell into distinct groups when taxa were categorized three ways—by phylum, feeding mode, and feeding anatomy—indicating that both taxonomic and trait‐based approaches are useful for describing the trophic diversity of gelatinous zooplankton. Even when gelatinous specimens cannot be identified taxonomically, their diets likely resemble those of taxa sharing the same feeding mode or anatomy. These insights refine our knowledge of marine food webs and facilitate the incorporation of these ubiquitous members of the food web into ecosystem models.
Abstract Groundwater dissolved oxygen (DO) variability in coastal systems remains poorly understood despite its importance for biogeochemical cycling and ecosystem modeling. This study investigates temporal variability in groundwater DO and its hydro‐climatic drivers across timescales (hourly to seasonal) in a coastal floodplain at Beaver Creek, Washington, USA, a site transitioning from a freshwater forest to brackish tidal wetland following restoration of tidal influence. Using 5 years of high‐frequency (5‐min) hydro‐meteorological and continuous groundwater DO data, we applied wavelet and information theory analyses to disentangle the role of different drivers (e.g., groundwater levels, temperature, precipitation, among others) on DO dynamics. Monitoring was initiated 5 years after the site was restored but prior to subsurface conditions reaching a new steady state. We found that DO pulses related to tidal flooding events were most frequent during earlier water years, dominated by hourly, daily and multiday variability. In later years both the frequency and magnitude of these DO pulses decreased, resulting in more prolonged subsurface anoxia. These shifts in DO patterns reflect gradually changing subsurface biogeochemical conditions as the system continues to fully transition from lowland forest to brackish wetland 10 years after restoration. This study highlights the critical role of timescale‐specific analyses in understanding wetland biogeochemistry by identifying dominant drivers of DO variability and linking them to ecosystem transitions. Our scale‐aware approach offers a framework for evaluating ecosystem responses to climate change, sea‐level rise, and restoration efforts in tidal wetlands.
Abstract The C : N : P of nitrogen‐fixing cyanobacteria regulates phosphate‐limited nitrogen fixation in the ocean yet the causes and range in variation C : N : P is not well constrained. Here we quantify the C : N : P and underlying macromolecular composition of Crocosphaera . Crocosphaera is a nitrogen‐fixing cyanobacterium that substantively contributes to elemental biogeochemistry in the (sub)tropical oceans. We observed variation in C : N : P and macromolecular composition over the photoperiod, across two different sized phenotypes and with phosphate concentration. In both phenotypes, C : N is ~ 1.3‐fold higher in the day than the night due to increasing carbohydrate in the smaller phenotype and increasing lipid in the larger phenotype during the day and increasing protein in both phenotypes at night. Detectable levels of surface adsorbed phosphorus were only observed at night. The two sized phenotypes differed in macromolecular allocation: the smaller phenotype had a higher proportion of carbon to DNA, RNA, and chlorophyll a while the larger phenotype was higher in lipids relative to carbohydrates. The largest variation in C : N : P arose with changes in phosphate concentration. Decreasing phosphate in the media from 50 to 0.5 μ M induced a 27‐fold decrease in cellular P, increasing molar N : P from ~ 2 to between 41 and 64 and C : P from ~ 15 to between 335 and 484 across the phenotypes. Much of these changes can be attributed to changes in polyphosphate content and secondarily DNA content. The accumulation and storage of polyphosphate under higher phosphate concentrations could temporarily increase Crocosphaera 's capacity to fix nitrogen when phosphate is scarce.
Abstract During the summer (June–August), marine heatwaves (MHWs) frequently occur in China's northern and eastern seas, including the Bohai Sea, Yellow Sea, and northern East China Sea. As a prominent marine environmental concern, these events have garnered widespread societal attention. However, the predictive capacity for such events remains constrained, underscoring the urgent need to comprehensively unravel the physical mechanisms governing their occurrence. In this study, we employ the Regional Ocean Modeling System to explore the local forcing factors driving MHW genesis. Our results reveal that the formation of summer MHWs is jointly determined by surface net heat fluxes, oceanic advection, and vertical mixing, with their relative contributions varying significantly across geographical locations. The formation of summer MHWs is closely related to surface wind stress anomalies. Under the background of weakened wind forcing, the temperature rise during the heat accumulation phase of MHWs is primarily driven by increased solar radiation, reduced cloud cover, and shoaling of the mixed layer. The suppression of vertical mixing further enhances heat accumulation in regions with water depth exceeding 50 m. These findings advance our understanding of the formation mechanisms of summer MHWs in China's northern and eastern seas, while improving the predictive capacity for such events.
Abstract Coastal estuaries are hotspots of biogeochemical cycling, biodiversity, and sediment processing, yet the drivers of carbon cycle processes remain poorly constrained. Here, we elucidate the influence of hydrological connectivity on carbon biogeochemistry in the Indian Sundarban over successive monsoon seasons by comparing hydrologically connected channels with perennial freshwater flow to channels isolated from feeding rivers. Results demonstrate dissolved organic carbon (DOC) and particulate organic carbon (POC) varied significantly with both season and connectivity. Dissolved organic carbon peaked pre‐monsoon and POC during the monsoon, with higher concentrations in hydrologically connected sites. Dissolved inorganic carbon (DIC) declined during the monsoon season but showed no connectivity effect. Elevated DOC relative to conservative mixing was attributed to freshwater runoff or groundwater input. Isotope data (δ 13 C) indicated POC respiration dominated during pre‐ and post‐monsoon, while DOC flocculation during the monsoon controlled POC dynamics, particularly in connected sites. Carbonate dissolution primarily regulated pre‐monsoon DIC, while organic matter degradation dominated in the monsoon and post‐monsoon periods. CO 2 efflux, measured across all sites, was consistently a source to the atmosphere and two to four times higher in connected channels, with higher turbulence driving maximum fluxes. Our findings demonstrate that hydrological connectivity fundamentally structures estuarine carbon cycling, lowering organic carbon concentrations and enhancing CO 2 fluxes. Shifts in global coastal delta sediment dynamics, in association with anthropogenic river management, therefore, have the potential to significantly alter delta carbon dynamics on a global scale.
Ecosystem transitions from bare to vegetated states often stall at early stages, before the biogeomorphic feedbacks needed for further expansion take hold. In aquatic systems, this bottleneck is especially common where inundation and hydrodynamic conditions may impose strong abiotic filters on pioneer establishment. Here, we integrate a manipulative field experiment with a simple probabilistic model to test whether tidal creeks, ubiquitous geomorphic features in tidal flats, can help overcome this bottleneck during early marsh assembly. In plots adjacent to experimentally created tidal creeks, transplanted seedlings of the pioneer halophyte Tripolium pannonicum had similar to 20% higher survival, grew taller, and were similar to 50% more likely to flower within a single growing season than seedlings in no-creek controls. Using the field-derived survival and flowering differences to estimate potential local seed supply, model simulations predicted higher recruitment probability and a shorter expected time lag to recruitment. Together, our findings demonstrate that geomorphic features can provide local footholds for pioneers and thereby contribute to early marsh assembly. These results emphasize the need to include geomorphic heterogeneity as a design principle of restoration strategies, improving recruitment conditions before vegetation feedbacks become established.
Phytoplankton blooms in tidally energetic estuaries are typically short-lived, yet the mechanisms driving their rapid onset and abrupt collapse remain poorly understood. Nutrient enrichment alone cannot account for these rapid boom-bust cycles, pointing to the potential regulatory role of periodic forcings such as tidal cycles in governing bloom dynamics. Here, we used a high-resolution three-dimensional physical-biogeochemical coupled model, validated with field observations, to investigate a transient bloom in Xiamen Bay, a eutrophic subtropical embayment. Bloom initiation was favored by neap-tide stratification and optimal temperature-light conditions, but subsequent spring tides induced rapid decline through turbulent disruption, vertical export into light-limited layers, and offshore advective loss. Diagnostic budget analyses revealed that although biological production remained positive, it was consistently outweighed by physical export, underscoring the primacy of biomass retention over nutrient supply in sustaining blooms. Despite persistent nitrogen excess, bloom resilience was further constrained by phosphorus depletion, light dilution, and episodic wind forcing. Spatial heterogeneity further shaped bloom trajectories, with semi-enclosed sub-basins supporting local growth while open areas were dominated by transport processes. Together, these results support a retention-controlled framework for bloom regulation in macrotidal estuaries, in which the spring-neap cycle acts as a hierarchical temporal regulator governing the balance between production and loss. This shift from nutrient-centric to retention-mediated controls helps explain why eutrophic estuaries often host short-lived blooms and provides a generalized mechanistic basis for interpreting bloom variability in tidally energetic coastal environments.
Trophic subsidies are resources that cross ecosystem boundaries, influencing the structure and function of recipient food webs. Widespread regulation of rivers for human consumptive use has profoundly altered natural flow regimes, decoupling donor-recipient dynamics between freshwater and marine ecosystems. We explored trophic subsidies to the Southern Indian Ocean from a highly regulated river during a 1 in 66-year flood by comparing delta 15N, delta 13C and delta 34S values of three marine trophic guilds sampled across the flood plume and at geographically isolated reference locations. Secondary and tertiary consumers collected within the flood plume were delta 15N enriched compared to reference animals and isotopic niche overlap declined across higher trophic levels (24% and 6% respectively). For both yellow-eye mullet (Aldrichetta forsterii-a secondary consumer) and Australasian snapper (Chrysophrys auratus-a tertiary consumer), there was no overlap in isotopic niche between flood plume and reference animals. Terrestrial contributions to marine animal biomass in the flood plume varied by trophic level and subsidies were highest among secondary consumers (35% compared to 22% for reference animals). Terrestrial contributions to tertiary consumers (29%) did not significantly diverge from reference estimates (21%), as evidenced by overlapping 95% credible intervals. This modest difference likely stems from a temporal mismatch between the flood peak and slower isotopic turnover rates among large predators. Our results emphasize that dietary integration reflected in secondary consumers provided the most reliable subsidy estimates due to exposure duration and representative body mass. Here, we demonstrate significant trophic subsidies resulting from the temporary re-establishment of river-marine coupling in a highly regulated river. Our findings provide quantitative empirical support for trophic ecological theory and underpin the importance of managing freshwater-marine linkages in the face of anthropogenic pressures.
Abstract Salinity maximum intrusions, subsurface layers of anomalously salty and warm continental slope water moving onto the continental shelf along the thermocline, are recurring features over the Northeast US Shelf and represent an important cross‐shelf exchange mechanism. While their physical characteristics have been described, the biological composition and ecological role of these intrusions remain poorly understood. Here, we combine multidisciplinary physical, biological, and biogeochemical observations from summer 2023 to provide direct evidence that salinity maximum intrusions advect offshore biological communities onto the continental shelf, focusing on an event that ranked among the strongest recorded in terms of salinity anomaly and spatial extent. The intrusion layer coincided with distinct acoustic scattering layers containing amphipods and larvae of shrimp, crab, and fish. Several offshore phytoplankton taxa of different cell sizes including Prochlorococcus , Trichodesmium colonies, and mixotrophic dinoflagellates were also observed, with rhizarians the only small zooplankton consistently present within the intrusion layer. The presence of flatfish and crustacean larvae highlights the role of intrusions in early life‐history connectivity, while amphipod aggregations—likely linked to elevated food supply and reproductive demand—suggest that intrusions can also act as feeding hotspots. With their increasing frequency and shoreward extent, salinity maximum intrusions emerge as a dynamic mechanism shaping community composition and mediating cross‐shelf biological connectivity on the Northeast US Shelf.
Intertidal organisms are exposed to extreme and variable thermal conditions due to periodic aerial exposure by tides. For sessile species that cannot seek refuge, heat stress is strongly influenced by the timing of low tides, which in semidiurnal tidal systems is governed by the spring-neap tidal cycle. Here, we deployed biomimetic loggers, designed to replicate body temperature of the mussel Mytilus edulis, at two climatologically similar yet tidally distinct sites in Wales, UK, to examine how interactions between climate and tidal phasing regulate intertidal heat stress. Despite comparable weather conditions, South Wales mussels-exposed during midday spring low tides-experienced daily maximum body temperatures over 3 degrees C higher compared to North Wales, where exposure occurred during morning and evening spring low tides. Consequently, South Wales mussels exceed critical temperature thresholds more frequently. Based on the observations, we developed and validated a mussel body temperature model incorporating readily available tidal and climatic data, which accurately reproduced observed logger temperatures and successfully simulated a 2018 mass mortality event in the English Channel. Model experiments showed that tidal phasing can modulate 95th-percentile daily maxima by up to 5.5 degrees C, with midday spring low tides producing the warmest possible conditions. Long-term simulations (1990-2023) further revealed a 2 to 2.5-fold increase in extreme temperature exposure since 2020. These results demonstrate that tidal characteristics in semidiurnal systems can amplify or mitigate intertidal thermal stress as strongly as local climate, and that simple, process-based models can forecast heat exposure and ecological vulnerability under future climate change.
Abstract Summer nitrification's role in nitrate assimilation remains poorly quantified in the high‐latitude Southern Ocean. This study presents the first nitrate δ 15 N and δ 18 O data from the rapidly melting Amundsen Sea, showing that nitrification is active throughout the continental shelf mixed layer, while nitrate assimilation dominates in adjacent open ocean waters. Box modeling estimates that nitrification supports 20 ± 14% of mixed‐layer nitrate assimilation, with no continental shelf and open ocean difference. Redundancy analysis indicates that nitrification covaries with multiple factors, with particulate nitrogen being the strongest environmental predictor, suggesting a potential role for ammonium availability in shaping nitrification patterns. The isotope effect of nitrate assimilation varies spatially, with lower values on the continental shelf, potentially related to increased nitrification and iron availability. These findings fill a critical gap by quantifying the role of mixed‐layer nitrification in nitrate assimilation and identifying key environmental correlates of nitrification variability in the high‐latitude Southern Ocean.
Abstract Diatoms and copepods are dominating and diverse groups of phytoplankton and zooplankton, respectively. Diatoms account for 25–40% of ocean primary production, and their main predators, copepods, are arguably the most abundant group of metazoans in the ocean, typically accounting for ~ 80% of zooplankton biomass. The two groups have co‐existed in the pelagic for maybe > 200 million years, where they have engaged in what appears to be a never‐ending evolutionary arms race. The arms race includes the evolution in diatoms of a thick silicious shell, the frustule, with a delicate nanostructure that makes it hard to break, the production of toxins that may deter copepod grazing, the ability to change colony size to get outside the prey size spectrum of copepod grazers, and the potential to form rapidly sinking aggregates that allow the diatoms to rescue from predators in the ocean depths or sediments. These defenses are all inducible, that is, they are harnessed or strengthened in response to diffusible cues from copepod grazers. In all cases, copepods have evolved anti‐defense mechanisms that allow them to at least partly overcome the defenses and/or responses that protect the copepods against poisoning and mechanical damage. We argue that the evolutionary arms race between diatoms and copepods is key to their evolutionary success in terms of abundance and diversity, and that it has partly shaped the pivotal role of diatoms and copepods in the biological carbon pump and carbon sequestration in the ocean.
Located at the land-ocean interface, coastal lagoons are specifically vulnerable to increasing threats from anthropogenic activities and climate change. Understanding the hydrological and ecological responses of these lagoon systems to global and local changes is essential. In this study, the spatial and seasonal (wet and dry seasons) variations of water level, salinity, nutrients, and ecosystem metabolism are investigated to understand the impacts of environmental changes on fish and invertebrates in Ambinanibe coastal lagoon (southeast Madagascar). Our results indicate that Ifaho River flow is the main driver of ecological functioning in the Ambinanibe lagoon. Seasonal variations in freshwater inflow directly affect salinity, nutrient concentrations, dissolved oxygen, and sediment dynamics. Changes in river discharge and lagoon-ocean connectivity also drive shifts in the trophic interactions and community structure of fish and invertebrates, demonstrating the strong sensitivity of lagoon ecosystems to hydrological variability. Overall, this study provides a robust scientific basis for understanding and predicting future ecological responses to changes in freshwater inflow, and for mitigating the ecological impacts of climate change and anthropogenic pressures.
Oxygen is critical for nearly all life on Earth, including aquatic species that breathe dissolved oxygen in both freshwater and marine systems. The rapid, global, and anthropogenic loss of dissolved oxygen known as "aquatic deoxygenation" threatens life in these environments, the human communities that depend on them, and Earth system stability long-term. Recognizing the important and increasingly widespread effects of aquatic deoxygenation, scientists have proposed that it be added to the planetary boundary framework, which is designed to capture the wider envelope of Earth-system conditions that support a "safe operating space for humanity." Here, we argue that the planetary boundary framework should include maintenance of Earth's aquatic ecosystems and thus dissolved oxygen conditions. We synthesize important, in some cases poorly understood, interactions and feedbacks that exist between deoxygenation and all nine of the established planetary boundaries. We find that aquatic deoxygenation interacts with and extensively modulates other boundary processes, including climate change, nutrient loading, biodiversity loss, and aerosol loading. Subsequently, we identify and describe four indicators that can be used to assess the status of aquatic deoxygenation and eventually define a global boundary for it within the framework. Given these interactions and current rates of oxygen loss, we argue that aquatic deoxygenation is approaching an "unsafe space," with Earth-system impacts that are likely to be irreversible in our lifetimes. We discuss the wider societal significance of this research, including applications to the framework, future analyses, policy-making, and management.
Zooplankton plays an important role in the biological carbon pump, and zooplankton biomass and community structure can have a large influence on the sedimentation/remineralization balance of the water column. We investigated the potential effects of zooplankton community structure and eco-physiology on the export and attenuation of vertical flux during an early North Atlantic spring bloom, using Calanus finmarchicus as a representative of large vertically migrating calanoids that primarily feed on suspended phytoplankton and produce large fast sinking fecal pellets, and Microsetella norvegica, Oncaea/Triconia spp. and Oithona spp. as representatives of aggregate- and detritus-feeding copepods. We measured (1) diurnal changes in the pellet production, egg production and respiration rates of Calanus finmarchicus and (2) weight-specific egg production of egg-carrying non-calanoid copepods and combined these with (3) the vertical distribution of copepod biomass and species composition. Our results demonstrated many-fold differences in the carbon demand of the copepod community over a few weeks of winter-spring transition, as well as many-fold differences in the vertical profiles of particle production vs. degradation depending on the zooplankton community structure.
