John M. Klinck

Environmentally transmitted pathogens in marine ecosystems are regulated through ecological interactions that influence encounter rates and therefore transmission between potential hosts. In aquatic suspension-feeders, for example, host density can simultaneously moderate both pathogen encounters and transmission efficiency. Here we develop a mechanistic model that incorporates saturating pathogen uptake, host competition, and host density-dependent limitation of environmental pathogen availability to investigate how these interacting processes shape disease dynamics. Using a next-generation matrix approach, we derive the basic reproduction number and establish the local stability of the disease-free equilibrium. Analytical results reveal that pathogen invasion potential and epidemic amplification are maximized at intermediate host densities, emerging naturally from the balance between host interference and environmental pathogen depletion rather than from imposed density-dependent transmission functions. Complementary numerical simulations confirm the analytical predictions and demonstrate that infection prevalence, epidemic size, and effective transmission all exhibit pronounced non-monotonic responses to host density. These findings provide a mechanistic framework for understanding how ecological feedbacks can generate maxima for pathogen transmission and epidemic risks observed in environmentally-transmitted marine diseases.

Recent studies have shown that the Indian Ocean is warming significantly, but how this warming impacts primary production is largely unresolved due to a relative lack of depth‐resolved biological observations. In this study, we have used Biogeochemical‐Argo data from 2013 to 2022, comprising over 9,000 individual profiles, to examine regional patterns and trends in depth‐integrated chlorophyll, depth‐integrated net primary production and stratification in the northern and Equatorial Indian Ocean. Our analysis shows that water column stratification is increasing in the majority of the study area, with the highest rate of increase observed in the western Bay of Bengal. At the same time, we find that depth‐integrated chlorophyll and depth‐integrated net primary production show an increasing trend in most parts of the Bay of Bengal, the western Arabian Sea, and some parts of the Equatorial Indian Ocean. However, the eastern Arabian Sea, the northern Bay of Bengal, and other parts of the Equatorial Indian Ocean have experienced a decrease in depth‐integrated chlorophyll and net primary production. The Indian Ocean Dipole and El Niño Southern Oscillation were found mostly to be weakly negatively correlated with the depth‐integrated chlorophyll and depth‐integrated net primary production in the northern Indian Ocean. Our results show that depth‐integrated chlorophyll and depth‐integrated net primary production are not strongly or consistently correlated with stratification within our study region, suggesting that the projected increases in stratification with ocean warming in this region may not drive concurrent reductions in primary production.

Offshore wind energy development on the Mid‐Atlantic Bight (MAB) portion of the Northwestern Atlantic continental shelf could have adverse impacts on the future of the Atlantic surfclam, Spisula solidissima , fishery. The current and potential future areas designated for offshore wind energy development overlap with the present‐day and projected Atlantic surfclam fishing grounds and so could limit the fishery. Fishery impacts imposed by displacement of fishing outside wind farm areas and possible restrictions on vessel transit through the wind farms were simulated using a spatially explicit fishery model. The distribution of catch, hours fished, landings per unit effort (LPUE), time at sea, fishing mortality, and the number of fishing trips were projected for five time periods encompassing the period of 2016–2055. Simulations showed a significant decline in the mean of all fishery metrics (apart from LPUE) as the area of wind farm restrictions increased in scale. Impacts were consistently larger when vessel transit through and fishing within offshore wind areas were prohibited. Impacts were also larger for MAB regions off New Jersey and Delmarva than regions farther north and east. These simulations highlight the necessity of evaluating future conditions as warming temperatures shift the surfclam range relative to the immobile wind farm locations. The offshore wind industry must consider projected long‐term impacts of developmental expansion on surrounding sedentary benthic species and the commercially important fisheries that rely on them.

The Atlantic surfclam, Spisula solidissima , and ocean quahog, Arctica islandica , are biomass dominant bivalve species on the eastern North American continental shelf, both supporting lucrative commercial fisheries in the Mid‐Atlantic with a combined value of about $53.6 million in ex‐vessel revenue per year. The thermal tolerance of Atlantic surfclam is generally below 20 °C, whereas the boreal ocean quahog resides in colder waters maintained by the Mid‐Atlantic Bight Cold Pool. Climate‐induced warming of bottom water temperatures is thought to be linked to the observed distributional shift of the Atlantic surfclam population into waters historically dominated by ocean quahogs. As climate change is expected to continue, this study investigated the future distributions of the two species from years 2016 to 2095 using projected bottom water temperatures and a temperature‐dependent population dynamics model. Simulations show the progressive colonization of Atlantic surfclams offshore into the region earlier occupied by the Cold Pool throughout the 79‐year projection, beginning between the mid‐2040s and mid‐2050s, effectively compressing ocean quahog habitat on all sides. Ocean quahogs are shown to be vulnerable to climate‐induced warming on both the southern, inshore, and offshore portions of the continental shelf, ultimately restricting their habitat by the end of the 21st century to the remaining core of the Cold Pool off Long Island. Atlantic surfclams, however, are likely to be less vulnerable to climate‐induced warming, ultimately increasing their geographic footprint across the MAB. Model projections indicate a large‐scale reorganization event of the continental shelf benthic community structure throughout the remainder of the 21st century.

The Atlantic surfclam, Spisula solidissima supports a lucrative commercial fishery in the Mid‐Atlantic Bight (MAB) worth roughly $30 million in revenue per year. Rapid climate change is expected to modify the geographic range of the Atlantic surfclam, with consequences for the surfclam fishery. This study evaluated fishery‐based indicators projected from 2020 through 2095 based on anticipated changes in the geographic range and biomass of the Atlantic surfclam, using a Spatially Explicit, agent‐based Fisheries and Economics Simulator (SEFES). Simulations generally showed a positive trend in Atlantic surfclam biomass throughout the next three‐quarters of the 21 ^st century as the clam's range continues to shift offshore and northward along the continental shelf. A general decrease in fishing mortality rate is projected given the present fleet capacity, with a simultaneous increase in catch and landings per unit effort (LPUE), signaling future potential growth in the surfclam fishery. Regionally, forecasts show biomass expanding into deeper waters particularly off New Jersey, Long Island, and southern New England starting in the early 2050s, whereas populations on Georges Bank and off Delmarva gradually decline. Trends in time spent fishing, catch, and LPUE parallel those of biomass in each region. These results can inform managers and business interests that rely on this fishery, as well as other users of the continental shelf, to provide a basis for the development of anticipatory management for the socio‐ecological and economic impacts that may result from future changes in the Atlantic surfclam range and carrying capacity consequent of climate change.

While there is evidence for an acceleration in global mean sea level (MSL) since the 1960s, its detection at local levels has been hampered by the considerable influence of natural variability on the rate of MSL change. Here we report a MSL acceleration in tide gauge records along the U.S. Southeast and Gulf coasts that has led to rates (>10 mm yr⁻¹ since 2010) that are unprecedented in at least 120 years. We show that this acceleration is primarily induced by an ocean dynamic signal exceeding the externally forced response from historical climate model simulations. However, when the simulated forced response is removed from observations, the residuals are neither historically unprecedented nor inconsistent with internal variability in simulations. A large fraction of the residuals is consistent with wind driven Rossby waves in the tropical North Atlantic. This indicates that this ongoing acceleration represents the compounding effects of external forcing and internal climate variability.

Organisms increase in size over time (age) due to excess assimilation over metabolic (respiration) energy demands. Most organisms reach a maximum size with increasing age as gain and loss balance. The von Bertalanffy length-at-age relationship, which is commonly used in fishery assessment calculations, imposes such a maximum size. However, some fished species, such as ocean quahogs, Arctica islandica, are long lived and continue to grow at old age. The Tanaka age-at-length relationship has continued growth at old age, but is rarely used in stock assessment models. A modified form of the von Bertalanffy model is presented, which mimics the continued growth at old age of the Tanaka model by allowing the growth parameter (K) to decline with age. This form is suitable for inclusion in stock assessment models based on von Bertalanffy. The proposed model matches Tanaka curves with precision appropriate for the scatter of data used to fit the curves. The observations of ocean quahog length at age and growth rate from New Jersey and Georges Bank demonstrate the ability of the modified von Bertalanffy relationship to represent continued growth at old age for this fished species. Simulated data generated with continued growth at old age were fit with the Stock Synthesis model (SS3). Results comparing traditional and modified growth relationships showed that the original von Bertalanffy model can reasonably approximate modest nonasymptotic growth as long as the number of observations is sufficient to constrain the parameter values.

While there is evidence for an acceleration in global mean sea-level (MSL) since the 1960s, its detection at local levels has been hampered by the considerable influence of natural variability on the rate of MSL change. Here we report an MSL acceleration in tide gauge records along the U.S. Southeast and Gulf coasts that has led to rates (>10 mmyr-1 since 2000) that are unprecedented in at least 120 years. We show that this acceleration is primarily induced by an ocean dynamic signal exceeding the externally forced response from historical climate model simulations. However, when the simulated forced response is removed from observations, the residuals are neither historically unprecedented nor inconsistent with unforced variability in simulations. Furthermore, a large fraction of the residuals can be explained by wind-driven Rossby waves in the tropical North Atlantic. This indicates that the acceleration represents the compounding effects of external forcing and internal climate variability.

Diel vertical migration (DVM) is common in zooplankton populations worldwide. Every day, zooplankton leave the productive surface ocean and migrate to deepwater to avoid visual predators and return to the surface at night to feed. This behavior may also help retain migrating zooplankton in biological hotspots. Compared to fast and variable surface currents, deep ocean currents are sluggish, and can be more consistent. The time spent in the subsurface layer is driven by day length and the depth of the surface mixed layer. A subsurface, recirculating eddy has recently been described in Palmer Deep Canyon (PDC), a submarine canyon in a biological hotspot located adjacent to the West Antarctic Peninsula. Circulation model simulations have shown that residence times of neutrally buoyant particles increase with depth within this feature. We hypothesize that DVM into the subsurface eddy increases local retention of migrating zooplankton in this feature and that shallow mixed layers and longer days increase residence times. We demonstrate that simulated vertically migrating zooplankton can have residence times on the order of 30 days over the canyon, which is five times greater than residence times of near‐surface, nonmigrating zooplankton within PDC and other adjacent coastal regions. The potential interaction of zooplankton with this subsurface feature may be important to the establishment of the biological hotspot around PDC by retaining food resources in the region. Acoustic field observations confirm the presence of vertical migrators in this region, suggesting that zooplankton retention due to the subsurface eddy is feasible.