A siliceous arms race in pelagic plankton.

Coevolution between predator and prey plays a central role in shaping the pelagic realm and may have significant implications for marine ecosystems and nutrient cycling dynamics. The siliceous diatom frustule is often assumed to have coevolved with the silica-lined teeth of copepods, but empirical evidence of how this relationship drives natural selection and evolution is still lacking. Here, we show that feeding on diatoms causes significant wear and tear on copepod teeth and that this leads to copepods becoming selective feeders. Teeth from copepods feeding on thick-shelled diatoms were more likely to be broken or cracked than those feeding on a dinoflagellate. When fed a large diatom, all analyzed teeth had visible wear. Our results underscore the importance of the predator-prey arms race as a driving force in planktonic evolution and diversity.

Impacts of salinity stress induced by ballast water discharge on the ecosystem of shanghai port, China.

Large quantities of marine ballast water discharged by ocean-going vessels can cause salinity increases in freshwater ports, which in turn negatively affects indigenous plankton in the ports. In this study, we investigated the impacts of marine ballast water discharge on the plankton community in a freshwater wharf through field surveys. It was found that salinity stress caused reductions in community indicators such as plankton community composition, abundance and diversity, thus threatening the structure and function of the plankton community in the wharf. In terms of the impact range, the salinity stress had a significant effect on all plankton in the waters near the discharge point and the phytoplankton in the waters 50 m from the discharge point, but had no significant effect on the plankton in the waters further away. Ballast water discharge also caused a significant decrease in the alpha diversity and richness of the plankton community but had no significant effect on the evenness of the plankton community. Moreover, phytoplankton were more tolerant of salinity changes than zooplankton in our study. This study provides an ecological reference for the scientific management of marine ballast water discharge and the risk of exogenous nutrient inputs to freshwater ecosystems.

Effect of plasma-activated water on planktonic and biofilm cells of Vibrio parahaemolyticus strains isolated from cutting board surfaces in retail seafood markets.

AIMS: This research aimed to analyze cutting board surfaces in seafood markets to find Vibrio parahaemolyticus, assess the isolates' ability to form biofilms, generate and evaluate characteristics of plasma-activated water (PAW), and compare the effect of PAW on planktonic and biofilm cells of the isolated V. parahaemolyticus strains. METHODS AND RESULTS: A total of 11 V. parahaemolyticus strains were isolated from 8.87% of the examined cutting boards. Biofilm-forming ability was evaluated for these isolates at temperatures of 10°C, 20°C, and 30°C using crystal violet staining. Four strains with the highest biofilm potential were selected for further analysis. The pH of the PAW used in the study was 3.41 ± 0.04, and the initial concentrations of hydrogen peroxide, nitrate, and nitrite were 108 ± 9.6, 742 ± 61, and 36.3 ± 2.9 µM, respectively. However, these concentrations decreased significantly within 3-4 days during storage at room temperature. PAW exhibited significant antimicrobial effects on V. parahaemolyticus planktonic cells, reducing viable bacteria up to 4.54 log CFU/ml within 20 min. PAW also reduced the number of biofilm cells on stainless steel (up to 3.55 log CFU/cm2) and high-density polyethylene (up to 3.06 log CFU/cm2) surfaces, although to a lesser extent than planktonic cells. CONCLUSIONS: PAW exhibited significant antibacterial activity against V. parahaemolyticus cells, although its antibacterial properties diminished over time. Furthermore, the antibacterial activity of PAW against biofilm cells of V. parahaemolyticus was less pronounced compared to the planktonic cells. Therefore, the actual effectiveness of PAW in seafood processing environments can be affected by biofilms that may form on various surfaces such as cutting boards if they are not cleaned properly.

Spatiotemporal changes of pelagic food webs investigated by environmental DNA metabarcoding and connectivity analysis.

Environmental DNA metabarcoding (eDNA metaB) is fundamental for monitoring marine biodiversity and its spread in coastal ecosystems. We applied eDNA metaB to seawater samples to investigate the spatiotemporal variability of plankton and small pelagic fish, comparing sites with different environmental conditions across a coast-to-offshore gradient at river mouths along the Campania coast (Italy) over 2 years (2020-2021). We found a marked seasonality in the planktonic community at the regional scale, likely owing to the hydrodynamic connection among sampling sites, which was derived from numerical simulations. Nonetheless, spatial variability among plankton communities was detected during summer. Overall, slight changes in plankton and fish composition resulted in the potential reorganization of the pelagic food web at the local scale. This work supports the utility of eDNA metaB in combination with hydrodynamic modelling to study marine biodiversity in the water column of coastal systems. This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.

Ecological associations distribution modelling of marine plankton at a global scale.

Marine plankton communities form intricate networks of interacting organisms at the base of the food chain, and play a central role in regulating ocean biogeochemical cycles and climate. However, predicting plankton community shifts in response to climate change remains challenging. While species distribution models are valuable tools for predicting changes in species biogeography under climate change scenarios, they generally overlook the key role of biotic interactions, which can significantly shape ecological processes and ecosystem responses. Here, we introduce a novel statistical framework, association distribution modelling (ADM), designed to model and predict ecological associations distribution in space and time. Applied on a Tara Oceans genome-resolved metagenomics dataset, the present-day biogeography of ADM-inferred marine plankton associations revealed four major biogeographic biomes organized along a latitudinal gradient. We predicted the evolution of these biome-specific communities in response to a climate change scenario, highlighting differential responses to environmental change. Finally, we explored the functional potential of impacted plankton communities, focusing on carbon fixation, outlining the predicted evolution of its geographical distribution and implications for ecosystem function.This article is part of the theme issue 'Connected interactions: enriching food web research by spatial and social interactions'.

Taxis-driven complex patterns of a plankton model.

This paper reports an important conclusion that self-diffusion is not a necessary condition for inducing Turing patterns, while taxis could establish complex pattern phenomena. We investigate pattern formation in a zooplankton-phytoplankton model incorporating phytoplankton-taxis, where phytoplankton-taxis describes the zooplankton that tends to move toward the high-densities region of the phytoplankton population. By using the phytoplankton-taxis sensitivity coefficient as the Turing instability threshold, one shows that the model exhibits Turing instability only when repulsive phytoplankton-taxis is added into the system, while the attractive-type phytoplankton-taxis cannot induce Turing instability of the system. In addition, the system does not exhibit Turing instability when the phytoplankton-taxis disappears. Numerically, we display the complex patterns in 1D, 2D domains and on spherical and zebra surfaces, respectively. In summary, our results indicate that the phytoplankton-taxis plays a pivotal role in giving rise to the Turing pattern formation of the model. Additionally, these theoretical and numerical results contribute to our understanding of the complex interaction dynamics between zooplankton and phytoplankton populations.

Multilevel relations among plankton stitched together with an eco-evolutionary needle.

Power-law relationships between population abundances, energy use, and other factors are often referred to as macroecological scaling. A recent study convincingly shows that these relationships emerge from individual physiology but only after the population distribution is shaped by trophic interactions that are subject to both ecological and evolutionary pressures.

Long-term declines in chlorophyll a and variable phenology revealed by a 60-year estuarine plankton time series.

Long-term ecological time series provide a unique perspective on the emergent properties of ecosystems. In aquatic systems, phytoplankton form the base of the food web and their biomass, measured as the concentration of the photosynthetic pigment chlorophyll a (chl a), is an indicator of ecosystem quality. We analyzed temporal trends in chl a from the Long-Term Plankton Time Series in Narragansett Bay, Rhode Island, USA, a temperate estuary experiencing long-term warming and changing anthropogenic nutrient inputs. Dynamic linear models were used to impute and model environmental variables (1959 to 2019) and chl a concentrations (1968 to 2019). A long-term chl a decrease was observed with an average decline in the cumulative annual chl a concentration of 49% and a marked decline of 57% in winter-spring bloom magnitude. The long-term decline in chl a concentration was directly and indirectly associated with multiple environmental factors that are impacted by climate change (e.g., warming temperatures, water column stratification, reduced nutrient concentrations) indicating the importance of accounting for regional climate change effects in ecosystem-based management. Analysis of seasonal phenology revealed that the winter-spring bloom occurred earlier, at a rate of 4.9 ± 2.8 d decade-1. Finally, the high degree of temporal variation in phytoplankton biomass observed in Narragansett Bay appears common among estuaries, coasts, and open oceans. The commonality among these marine ecosystems highlights the need to maintain a robust set of phytoplankton time series in the coming decades to improve signal-to-noise ratios and identify trends in these highly variable environments.

Biogeographic response of marine plankton to Cenozoic environmental changes.

In palaeontological studies, groups with consistent ecological and morphological traits across a clade's history (functional groups)1 afford different perspectives on biodiversity dynamics than do species and genera2,3, which are evolutionarily ephemeral. Here we analyse Triton, a global dataset of Cenozoic macroperforate planktonic foraminiferal occurrences4, to contextualize changes in latitudinal equitability gradients1, functional diversity, palaeolatitudinal specialization and community equitability. We identify: global morphological communities becoming less specialized preceding the richness increase after the Cretaceous-Palaeogene extinction; ecological specialization during the Early Eocene Climatic Optimum, suggesting inhibitive equatorial temperatures during the peak of the Cenozoic hothouse; increased specialization due to circulation changes across the Eocene-Oligocene transition, preceding the loss of morphological diversity; changes in morphological specialization and richness about 19 million years ago, coeval with pelagic shark extinctions5; delayed onset of changing functional group richness and specialization between hemispheres during the mid-Miocene plankton diversification. The detailed nature of the Triton dataset permits a unique spatiotemporal view of Cenozoic pelagic macroevolution, in which global biogeographic responses of functional communities and richness are decoupled during Cenozoic climate events. The global response of functional groups to similar abiotic selection pressures may depend on the background climatic state (greenhouse or icehouse) to which a group is adapted.

Synergistic digestibility effect by planktonic natural food and habitat renders high digestion efficiency in agastric aquatic consumers.

A digestibility enhancing effect of natural food on stomachless fish model (Cyprinus carpio) was verified by fluorogenic substrate assays of enzymatic activities in experimental pond carp gut flush and planktonic food over a full vegetative season. Then compared with size-matched conspecific grown artificially (tank carp) and an advanced omnivore species possessing true stomach (tilapia, Oreochromis niloticus). Results suggested activities of digestive enzymes (except amylolytic) were significantly higher in pond carp (p ≤ 0.05) than in the size-matched tank carp. Even compared to tilapia, pond carp appeared superior (p < 0.05; proteolytic or chitinolytic activities) or comparable (p > 0.05; phosphatase or cellulolytic activities). Amylolytic, chitinolytic, and phosphatases activities in pond carp gut significantly increased (p ≤ 0.01) over season. Several orders-of-magnitude higher enzymatic activities were detected in planktonic natural food than expressed in carp gut. Amino acid markers in planktonic food revealed a higher share of zooplankton (microcrustaceans), but not phytoplankton, synchronized with higher activities of complex polysaccharide-splitting enzymes (cellulolytic and chitinolytic) in fish gut. Periods of clear water phase low in chlorophyll-a and nutrients, but high in certain zooplankton (preferably cladocerans), may create a synergistic digestibility effect in pond carp. We conclude aquatic ecosystem components (natural food, water, microbiota) enhance fishes' hydrolyzing capabilities of C/N/P macromolecules and even their complex polymers such as cellulose, chitin, and maybe phytate (to be validated), to the extent that being stomachless is not an issue. Aquatic nutritional ecologists may consider that laboratory-based understandings of digestibility may underestimate digestion efficiency of free-ranging fish in ponds or lakes.

Planktonic Duration of the Bryozoan Cyphonautes Larva and Limits on Growth Rate Imposed by Its Form-Limited Maximum Clearance Rate.

AbstractThe form of the cyphonautes larva of bryozoans changes little during development. The ciliated band that generates the feeding current increases nearly in proportion to body length, so that the maximum rate of clearing planktonic food from a volume of water becomes increasingly low relative to body protein. This development is unlike the other larvae that produce a feeding current with bands of simple cilia. The cyphonautes' growth rate has therefore been predicted to be unusually low when food is scarce. As predicted, cyphonautes larvae of a species of Membranipora starved at concentrations of food that supported growth of pluteus larvae. Comparisons between the cyphonautes and plutei of a sand dollar were for growth from first feeding to metamorphosis, with a mix of two algal species. Another comparison was for growth of cyphonautes at an advanced stage and plutei of a regular sea urchin at an early stage, with food in seawater at a reduced concentration. The low maximum clearance rate did not prevent rapid growth and development of some cyphonautes from egg through metamorphosis when food was abundant. Twenty-nine days for development to metamorphosis in the laboratory with abundant food was close to Yoshioka's estimate of larval duration from the time lag between adult zooid density and larval abundance in a population in the Southern California Bight. Despite individual variation in growth rates and other physiological and environmental influences, simple measures of larval form predicted the differences in larval performance: scarce food extended larval duration for the cyphonautes more than for plutei.

The ecological dynamics of Barra Bonita (Tietê River, SP, Brazil) reservoir: implications for its biodiversity / A dinâmica ecológica da represa de Barra Bonita: as implicações na sua biodiversidade

Barra Bonita reservoir is located in the Tietê River Basin - São Paulo state - 22° 29" to 22° 44" S and 48° 10° W and it is the first of a series of six large reservoirs in this river. Built up in 1963 with the aim to produce hydroelectricity this reservoir is utilized for several activities such as fish production, irrigation, navigation, tourism and recreation, besides hydroelectricity production. The seasonal cycle of events in this reservoir is driven by the hydrological features of the basin with consequences on the retention time and on the limnological functions of this artificial ecosystem. The reservoir is polymitic with short periods of stability. Hydrology of the basin, retention time of the reservoir and cold fronts have an impact in the vertical and horizontal structure of the system promoting rapid changes in the planktonic community and in the succession of species. Blooms of Microcystis sp. are common during periods of stability. Superimposed to the climatological and hydrological forcing functions the human activities in the watershed produce considerable impact such as the discharge of untreated wastewater, the high suspended material contributions and fertilizers from the sugar cane plantations. The fish fauna of the reservoir has been changed extent due to the introduction of exotic fish species that exploit the pelagic zone of the reservoir. Changes in the primary productivity of phytoplankton in this reservoir, in the zooplankton community in the diversity and organization of trophic structure are a consequence of eutrophication and its increase during the last 20 years. Control of eutrophication by treating wastewater from urban sources, adequate agricultural practices in order to diminish the suspended particulate matter contribution, revegetation of the watershed and riparian forests along the tributaries are some possible restoration measures. Another action that can be effective is the protection of wetlands...

A represa de Barra Bonita localizada na bacia do médio Tietê, Estado de São Paulo (22° 29" a 22° 44" S e 48° 10" W) é o primeiro de uma série de seis reservatórios de grande porte localizados nesse rio. Construída em 1963, com a finalidade de produção de energia elétrica, esta represa é utilizada atualmente também para produção de peixes, recreação, turismo, navegação e irrigação. O ciclo estacional de eventos nesse reservatório é dirigido, em grande proporção, pelas características hidrológicas da bacia hidrográfica com conseqüências nas funções limnológicas desse ecossistema. O reservatório é polimítico com curtos períodos de estabilidade vertical. A hidrologia da bacia hidrográfica, o tempo de retenção do reservatório e as frentes frias têm um papel fundamental na estrutura horizontal e vertical do sistema, produzindo rápidas alterações na comunidade planctônica e na sucessão de espécies do fitoplâncton, zooplâncton e bacterioplâncton. Florescimentos de Microcystis aeruginosa são freqüentes durante períodos de estabilidade térmica vertical. Atelomixia é também um fenômeno recorrente na represa de Barra Bonita. Os 114 tributários são elementos de heterogeneidade espacial na represa. Superpostas às funções de forças climatológicas e hidrológicas, as atividades humanas na bacia hidrográfica produzem considerável impacto, tais como a descarga de nitrogênio e fósforo de esgotos não tratados, materiais particulados e dissolvidos em suspensão, e fertilizantes provenientes das extensas plantações de cana-de-açúcar na bacia hidrográfica. A fauna iíctica apresentou inúmeras alterações, principalmente, devido à introdução de espécies exóticas de peixes que exploram a zona pelágica do reservatório. Alterações na produção primária do fitoplancton, na comunidade zooplanctônica e no bacterioplâncton, e na estrutura trófica, são uma das conseqüências da eutrofização e do seu aumento nos últimos 20 anos. Além disto, a toxicidade e a predação intrazooplanctônica...

Planktonic primary production in a tidally influenced mangrove forest on the Pacific coast of Costa Rica

The seasonal variation of planktonic primary productivity was measured during one year in the main channel in the interior part of the mangrove forest of the Estero de Morales (Estero de Punta Morales), a mangrove system located in the Golfo de Nicoya at the Pacific coast of Costa Rica. Samples were incubated at the surface, 0.5 m and 1.0 m depth and the [quot ]light and dark bottle technique[quot ] was employed. The annual gross primary productivity (PPg) was 457 and the net primary productivity (PPn) was 278 g C m(-2) a(-1). Daily PPg ranged from 0.29 to 3.88 and PPn from 0.12 to 2.76 g C m(-2) d(-1). The highest rates observed in May and September were due to red tide blooms. The seasonal variation of primary productivity inside the mangrove forest depends closely on the PP in the adjacent area of the upper Golfo de Nicoya. Obviously the PP was light-limited since the compensation depth in the ebb current was found at only 1 m depth. In the flood current it was somewhat deeper. The planktonic primary productivity inside the mangrove forest was completely restricted to the open channels. A simultaneous measurement demonstrated that PPn of the phytoplankton could not take place under the canopy of the mangroves. Additional studies on the time course of the oxygen concentration in the mouth of the main channel over 24 hrs demonstrated a relation between the O2 and the tidal curves. The ebb current had always lower O2 concentrations than the flood current, regardless of the time of the day. The difference to the foregoing high tide, however, was much smaller when the low tide occurred during the day. This indicates that under the canopy the net primary production and hence O2 liberation of the attached macro- and microalgae, together with the high PPn of the phytoplankton in the channels, helped the oxygen concentration not to decrease as far as during the night. Nevertheless it shows that the consumtion of organic material in the submersed part of the...

El Niño 1997-1998 impact on the plankton dynamics in the Gulf of Nicoya, Pacific coast of Costa Rica

The impact of the El Niño 1997-1998 phenomenom on plankton dynamics was studied during 1997 at the Punta Morales estuary, Gulf of Nicoya, Pacific coast of Costa Rica. The study covered dry season/transition and the rainy season. Phytoplankton (microphytoplankton > 30 microm and nanophytoplankton) were collected at two depths (50 and 10% light incidence) using a 5 L Niskin bottle, and samples taken to determine chlorophyll a. Temperature, salinity, oxygen, and Secchi depth were measured. Horizontal sub-surface zooplankton hauls were conducted with a conic zooplankton net of 0.49 m diameter and 280 microm mesh width, supplied with a flowmeter. Surface sea water temperature average was 29.9 +/- 0.9 degrees C, with a maximum of 31.5 degrees C in April and a minimun of 28 degrees C in March and October. Chlorophyll a concentration (phytoplankton net) averaged 3.1 +/- 1.7 mg/m3, with higher values during the rainy season and lower values during the transition. Nanophytoplankton chlorophyll a concentration averaged 2.5 +/- 1.2 mg/m3, with a maximum during the transition season. For both fractions there were significant differences between transition and rainy seasons, and for nanophytoplankton between dry and transition seasons (p < 0.05). In the last case, differences were explained by temperature. Herbivorous copepods dominated the abundance and biomass of zooplankton, with a biomass maximun of 167.3 in October and a minimun of 7.1 mg DW/m3 in December. These values are higher than those found some years ago in the same zone and those reported for some places in the Caribbean. The El Niño 1997-1998 phenomenon in the plankton dynamics appears to have produced a change in the phytoplankton structure. This is the first attempt to evaluate the possible impact of El Niño on the plankton dynamics of the Pacific coast of Central America.