Description: Modern reef-building corals sustain a wide range of ecosystem services because of their ability to build calcium carbonate reef systems. The influence of environmental variables on coral calcification rates has been extensively studied, but our understanding of their relative importance is limited by the absence of in situ observations and the ability to decouple the interactions between different properties. We show that temperature is the primary driver of coral colony (Porites astreoides and Diploria labyrinthiformis) and reef-scale calcification rates over a 2-year monitoring period from the Bermuda coral reef. On the basis of multimodel climate simulations (Coupled Model Intercomparison Project Phase 5) and assuming sufficient coral nutrition, our results suggest that P. astreoides and D. labyrinthiformis coral calcification rates in Bermuda could increase throughout the 21st century as a result of gradual warming predicted under a minimum CO2 emissions pathway [representative concentration pathway (RCP) 2.6] with positive 21st-century calcification rates potentially maintained under a reduced CO2 emissions pathway (RCP 4.5). These results highlight the potential benefits of rapid reductions in global anthropogenic CO2 emissions for 21st-century Bermuda coral reefs and the ecosystem services they provide.

Description: Modern reef-building corals sustain a wide range of ecosystem services because of their ability to build calcium carbonate reef systems. The influence of environmental variables on coral calcification rates has been extensively studied, but our understanding of their relative importance is limited by the absence of in situ observations and the ability to decouple the interactions between different properties. We show that temperature is the primary driver of coral colony (Porites astreoides and Diploria labyrinthiformis) and reef-scale calcification rates over a 2-year monitoring period from the Bermuda coral reef. On the basis of multimodel climate simulations (Coupled Model Intercomparison Project Phase 5) and assuming sufficient coral nutrition, our results suggest that P. astreoides and D. labyrinthiformis coral calcification rates in Bermuda could increase throughout the 21st century as a result of gradual warming predicted under a minimum CO2 emissions pathway [representative concentration pathway (RCP) 2.6] with positive 21st-century calcification rates potentially maintained under a reduced CO2 emissions pathway (RCP 4.5). These results highlight the potential benefits of rapid reductions in global anthropogenic CO2 emissions for 21st-century Bermuda coral reefs and the ecosystem services they provide.

Description: Parasites of phytoplankton influence phytoplankton bloom dynamics and may severely affect the type of food available for higher trophic levels. The incidence of parasitic infections generally is expected to increase across ecosystems worldwide under the scenario of global change. Herein we report on a massive parasite infection on two dominant diatoms of the austral winter bloom, namely Thalassiosira pacifica and Chaetoceros diadema, recorded during an extreme precipitation period in the Bahía Blanca Estuary, Argentina. The parasite infection was concomitant with a marked drop in water salinity and affected more than 40% of host cells. Although the parasite on C. diadema was not identified, the parasite on T. pacifica was most likely Pirsonia sp., a nanoflagellate with high host specificity. After the intense rainy period and the parasitic infection, the phytoplankton biomass dropped (by more than 80%) and the community structure shifted to one with smaller species (i.e. Thalassiosira curviseriata, T. hibernalis and T. minima). We discuss the implications that these modifications may have on the food web dynamics and the potential relationship between precipitation-driven modifications in water properties and the emergence of parasitism in coastal eutrophic environments.

Description: Highlights: • Picophytoplankton was able to grow under a wide range of environmental conditions varying seasonally. • Picophytoplankton variability was more marked in the bay than in the lagoon. • Picophytoplankton decreased in the lagoon under enhanced anthropogenic stress. • Synechococcus, the most abundant group of the community, was frequently present in both ecosystems during the monitoring. We investigated at the single cell level during 16months (June 2012 to September 2013) the temporal distribution of picophytoplankton (picoeukaryotes, Synechococcus and Prochlorococcus) communities in two contrasted ecosystems: the Bay of Bizerte characterised by an oligotrophic regime typical of the Mediterranean Sea and the Bizerte Lagoon that exhibits a mesotrophic/eutrophic state. We aimed at depicting seasonal variations and quantifying the relationships between the environmental factors and the structure and abundance of picophytoplankton communities. Results showed that picophytoplankton groups were able to grow under a wide range of environmental conditions varying seasonally, although their abundances and contributions to the total chlorophyll biomass significantly varied and showed importance in the Bay of Bizerte. Synechococcus was the most abundant group reaching 225*103 cells·cm-3 in the Bay and 278*103 cells·cm-3 in the lagoon. This group was present all over the year in both ecosystems. Structural equation model results pointed out a different configuration regarding the picophytoplankton environmental drivers. The complexity of the configuration, i.e. number of significant links within the system, decreased under enhanced eutrophication conditions. The less exposure to anthropogenic stress, i.e. in the Bay of Bizerte, highlight a larger role of nutrient and hydrological conditions on the seasonal variations of picophytoplankton, whereas a negative effect of eutrophication on picophytoplankton communities was unveiled in the Bizerte Lagoon. We stress that such influence may be exacerbated under expected scenarios of Mediterranean warming conditions and nutrient release in coastal ecosystems.

Description: Climate variability plays a central role in the dynamics of marine pelagic ecosystems shaping the structure and abundance changes of plankton communities, thereby affecting energy pathways and biogeochemical fluxes in the ocean. Here we have investigated complex interactions driven a climate-hydrology-plankton system in the southern East China Sea over the period 2000 to 2012. In particular, we aimed at quantifying the influence of climate phenomena playing out in tropical (El Nino 3.4) and middle-high latitudes (East Asia Winter Monsoon, EAWM, and Pacific Decadal Oscillation, PDO) on pelagic copepods. We found that the EAWM and El Nino 3.4 showed a non-stationary and non-linear relationship with local temperature variability. In the two cases, the strength of the relationship, as indexed by the wavelet coherence analysis, decreased along with the positive phase of the PDO. Likewise, the influence of EAWM and El Nino3.4 on copepods exhibited a non-stationary link that changed along with the PDO state. Indeed, copepods and EAWM were closely related during the positive phase, while the link copepods–El Nino 3.4 was stronger during the negative phase. Our results pointed out cascading effects from climate to plankton driven by the positive phase of the PDO through its effect on temperature conditions, and likely through a larger southward transport of nutrient-rich water masses to northern Taiwan and the Taiwan Strait. We suggest a chain of mechanisms whereby the PDO shapes interannual dynamics of pelagic copepods and highlight that these results have implications for integrative management measures, as pelagic copepods plays a prominent role in food web dynamics and for harvested fish in the East China Sea. © 2018 Molinero et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Description: Estuaries are among the most valuable aquatic systems in terms of their services to human welfare. They offer an ideal framework to assess multiscale processes linking climate and food web dynamics through the hydrological cycle. Resolving food web responses to climate change is fundamental to resilience management of these threatened ecosystems under global change scenarios. Here, we examined the temporal variability of the plankton food web in the Mondego Estuary, central Iberian Peninsula, over the period 2003 to 2012. The results pointed out a cascading effect from climate to plankton communities that follow a non-stationary behavior shaped by the climate variance envelope. Concurrent changes in hydrographic processes at the regional, that is, upwelling intensity, and local, that is, estuarine hydrology, scales were driven by climatic forcing promoted by the North Atlantic Oscillation; the influence of which permeated the physical environment in the estuary affecting both autotrophic and heterotrophic communities. The most conspicuous change arose around 2008 and consisted of an obvious decrease in freshwater taxa along with a noticeable increase in marine organisms, mainly driven by gelatinous zooplankton. The observed increase in small-sized cosmopolitan copepods, that is, Clausocalanus arcuicornis, Oithona plumifera, thermophilic species, that is, Penilia avirostris, and gelatinous zooplankton suggests a structural change in the Mondego plankton community. These results provide empirical support to the expectation that expanding climate variance changes plankton structure and functioning, likely fostering trophic interactions in pelagic food webs.

Description: Highlights • Increasing influence of multiple environmental drivers produces changes on the temporal variability of species. • The intensity and hierarchy of drivers acting upon organisms within alternative regimes of variability may differ. • We identified regimes of variability of phytoplankton and depicted cascading effects of multiple drivers in each period. • The number of factors driving the response of phytoplankton increased along time and produced the erosion of productivity patterns. • The hierarchy and interactions of drivers changed over time, revealing that management policies require constant update. Abstract Estuaries are among the most valuable aquatic systems by their services to human welfare. However, increasing human activities at the watershed along with the pressure of climate change are fostering the co-occurrence of multiple environmental drivers, and warn of potential negative impacts on estuaries resources. At present, no clear understanding of how coastal ecosystems will respond to the non-stationary effect of multiple drivers. Here we analysed the temporal interaction among multiple environmental drivers and their changing priority on shaping phytoplankton response in the Bahía Blanca Estuary, SW Atlantic Ocean. The interaction among environmental drivers and the number of significant direct and indirect effects on chlorophyll concentration increased over time in concurrence with enhanced anthropogenic stress, changing winter climate and wind patterns. Over the period 1978–1993, proximal variables such as nutrients, water temperature and salinity, showed a dominant effect on chlorophyll, whereas in more recent years (1993–2009) climate signals (SAM and ENSO) boosted indirect effects through its influence on precipitation, wind, water temperature and turbidity. Turbidity emerged as the dominant driver of chlorophyll while in recent years acted synergistically with the concentration of dissolved nitrogen. As a result, chlorophyll concentration showed a significant negative trend and a loss of seasonal peaks reflecting a pronounced reorganisation of the phytoplankton community. We stress the need to account for the changing priority of drivers to understand, and eventually forecast, biological responses under projected scenarios of global anthropogenic change.

Description: Aurelia aurita (Linneaus, 1758) is a cosmopolitan scyphozoan, probably the most investigated jellyfish in temperate and highly productive coastal ecosystems. Despite a prominent top-down control in plankton food webs, a mechanistic understanding of A. aurita population dynamics and trophic interactions has been barely addressed. Here we develop a food web dynamic model to assess A. aurita role in the seasonal plankton dynamics of the Kiel Fjord, southwestern Baltic Sea. The model couples low trophic level dynamics, based on a classical Nutrient Phytoplankton Zooplankton Detritus (NPZD) model, to a stage-resolved copepod model (referencing Pseudocalanus sp.) and a jellyfish model (A. aurita ephyra and medusa) as consumers and predators, respectively. Simulations showed the relevance of high abundances of A. aurita, which appear related with warm winter temperatures, promoting a shift from a copepod-dominated food web to a ciliate and medusa dominated one. The model captured the intraspecific competition triggered by the medusae abundance and characterized by a negative relationship between population density and individual size/weight. Our results provide a mechanistic understanding of an emergent trait such as size shaping the food web functioning, driving predation rates and population dynamics of A. aurita, driving its sexual reproductive strategy at the end of the pelagic phase.

Description: Acknowledged as among the worst invasive marine species, Mnemiopsis leidyi has spread through European Seas since the mid-1980's. Here we report a bimonthly survey conducted in 2010-11 in three lagoons (Bages-Sigean, Thau and Berre) and at two adjacent coastal stations (Sète and SOMLIT-Marseille) along the French Mediterranean coast. M. leidyi was present only in Berre and Bages-Sigean with maximum abundances observed in late summer. M. leidyi adults were present year round in Berre with the largest organisms (~6 cm) observed in April. In Bages-Sigean, they occurred in sufficient abundance to be recorded by fishermen between August and November. Multiple linear regressions highlighted that abundance in both lagoons was mainly influenced by direct effects of salinity and chlorophyll-a, and temperature to a lesser extent. While M. leidyi has not yet been recorded in Thau, the lagoon is continually monitored to detect the potential establishment of M. leidyi.

Description: Highlights: • The diatom PUA decadienal strongly impacted demographic traits of Pseudodiaptomus annandalei. • Decadienal negatively affected survival, development and reproduction in a dose-dependent manner. • Nauplii successfully molted to copepodites; however copepodites were not able to molt to the adult stage when exposed to decadienal. • Negative effects on female survival were not recorded beyond 6 days of exposure to decadienal suggesting an evolutionary adaptive response to PUA with time. • Progressive tolerance to decadienal suggest evolutionarily adaptive response to PUA with time. Abstract: The euryhaline calanoid copepod Pseudodiaptomus annandalei perennially occurs in tropical and subtropical brackish water ecosystems and harbors supporting harmful algal blooms. In the present paper we provide a quantitative assessment of the influence of the diatom-derived poly-unsaturated aldehyde (PUA), 2-trans-4-trans-decadienal on demographic traits of P. annandalei. The survival and reproduction of P. annandalei were recorded in life table experiments, using a cohort of adult males and females exposed to a range of concentrations (0.75, 1.5, 3 and 4.5 μM) of decadienal. Higher mortality of female cohorts and lower reproduction were recorded with increasing concentrations of decadienal (3 and 4.5 μM). The estimated survival time for cohort females (control: 9.7 days; 4.5 μM decadienal: 4.7 days) and developmental stages of copepods (control: 10.5 days; 4.5 μM decadienal: 1.0 days) in decadienal applied medium (Isochrysis galbana + decadienal) was significantly lower than those in control (only I. galbana). Detrimental effects further eroded recruitment by increasing naupliar mortality and impairing copepodite development to adulthood. Since P. annandalei is widely used in the aquaculture industry in Asia, the present results call for a limited use of PUA producing diatoms as algal food to avoid impairing copepod reproduction and development.