Copepod life strategy and population viability in response to prey timing and temperature : testing a new model across latitude, time, and the size spectrum

A new model ("Coltrane": Copepod Life-history Traits and Adaptation to Novel Environments) describes environmental controls on copepod populations via (1) phenology and life history and (2) temperature and energy budgets in a unified framework. The model tracks a cohort of copepods spawned on a given date using a set of coupled equations for structural and reserve biomass, developmental stage, and survivorship, similar to many other individual-based models. It then analyzes a family of cases varying spawning date over the year to produce population-level results, and families of cases varying one or more traits to produce community-level results. In an idealized global-scale testbed, the model correctly predicts life strategies in large Calanus spp. ranging from multiple generations per year to multiple years per generation. In a Bering Sea testbed, the model replicates the dramatic variability in the abundance of Calanus glacialis/marshallae observed between warm and cold years of the 2000s, and indicates that prey phenology linked to sea ice is a more important driver than temperature per se. In a Disko Bay, West Greenland testbed, the model predicts the viability of a spectrum of large-copepod strategies from income breeders with a adult size ~100 μgC reproducing once per year through capital breeders with an adult size > 1000 μgC with a multiple-year life cycle. This spectrum corresponds closely to the observed life histories and physiology of local populations of Calanus finmarchicus, C. glacialis, and Calanus hyperboreus. Together, these complementary initial experiments demonstrate that many patterns in copepod community composition and productivity can be predicted from only a few key constraints on the individual energy budget: the total energy available in a given environment per year; the energy and time required to build an adult body; the metabolic and predation penalties for taking too long to reproduce; and the size and temperature dependence of the vital rates involved

Eukaryotic and cyanobacterial communities associated with marine snow particles in the oligotrophic Sargasso Sea

Marine snow aggregates represent heterogeneous agglomerates of dead and living organic matter. Composition is decisive for their sinking rates, and thereby for carbon flux to the deep sea. For oligotrophic oceans, information on aggregate composition is particularly sparse. To address this, the taxonomic composition of aggregates collected from the subtropical and oligotrophic Sargasso Sea (Atlantic Ocean) was characterized by 16S and 18S rRNA gene sequencing. Taxonomy assignment was aided by a collection of the contemporary plankton community consisting of 75 morphologically and genetically identified plankton specimens. The diverse rRNA gene reads of marine snow aggregates, not considering Trichodesmium puffs, were dominated by copepods (52%), cnidarians (21%), radiolarians (11%), and alveolates (8%), with sporadic contributions by cyanobacteria, suggesting a different aggregate composition than in eutrophic regions. Composition linked significantly with sampling location but not to any measured environmental parameters or plankton biomass composition. Nevertheless, indicator and network analyses identified key roles of a few rare taxa. This points to complex regulation of aggregate composition, conceivably affected by the environment and plankton characteristics. The extent to which this has implications for particle densities, and consequently for sinking rates and carbon sequestration in oligotrophic waters, needs further interrogation

Stratification-mixing cycles and plankton dynamics in a shallow estuary (limfjord, denmark)

15 páginas, 9 figuras, 2 tablasThe biomass, production and consumption of phytoplankton, bacteria and zoo- plankton in a shallow Danish estuary (Limfjord) were analysed during a 9-day period. The water column changed between stratified and mixed conditions which influenced the dominant processes in the pelagic system. During strong stratification, phytoplank- ton was mainly controlled by microzooplankton grazing. A mixing event, which homogenized the water column, possibly provided food to a mussel-dominated benthic community. Concomitantly, zooplankton feeding and reproduction decreased. However, the nutrient input to the upper part of the water column during mixing and the subsequent stabilization provided the ideal conditions for the recovery of phytoplankton from the loss processes from previous days. Microzooplankton, which was also a significant consumer of bacteria throughout the sampling period, was not the only consumer controlling phytoplankton. The microbial food web was an important route for total plankton carbon during the study. However, the shorter food web increased in importance during mixing, possibly due to stronger benthic–pelagic coupling than during stratified periods. Stratification-mixing cycles, occurring during short-time periods, should be a key mechanism maintaining the benthic and pelagic communities in this shallow water systemThis work was funded by the EU project MABENE (grant EKV3-2001-00144). I.G.T. was supported by a FCT (Portuguese Foundation for Science and Technology) doctoral fellowship (SFRH/BD/11309/2002) and B.G.C. by a CSIC-ESF I3P fellowshipPeer reviewe

Lights and shadows of the feeding ecology of the small copepod Oithona

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainWithin zooplankton, copepods are the most abundant organisms in marine ecosystems. Copepods of the genus Oithona are present in polar, temperate, subtropical, and tropical waters; in epipelagic and mesopelagic environments; in estuaries, mangroves, continental shelves, and in the open ocean. They are often the most abundant copepod, and they play a key role in biogeochemical cycles in pelagic marine food webs. Despite their recognized ecological importance in pelagic environments, the genus Oithona is one of the least studied groups of copepods, and there are many unknown aspects of their biology, ecophysiology, and ecological role in marine ecosystems. Here we present results on the natural diet of Oithona spp. based on feeding experiments with adult females. We suggest that the ambush feeding behaviour of Oithona spp. defines the prey spectrum of their natural diet, since they feed on relatively few taxonomic groups comprising mainly motile organisms. In this presentation we will briefly review the known (lights) and unknown (shadows) aspects of the feeding ecology of Oithona spp., and add new insights based on comparative experiments conducted in tropical and polar watersPeer Reviewe

Can we use laboratory-reared copepods for experiments? A comparison of feeding behaviour and reproduction between a field and a laboratory population of Acartia tonsa

8 pagesMotility patterns and egg production were investigated in two populations of Acartia tonsa, field animals from the Öresund and laboratory animals from a 12-year-old (≈ 120 generations) culture. When observed in aquaria with a layer of Thalassiosira weissffogii in the middle, laboratory animals displayed weak aggregation behaviour, while field animals did not aggregate at all. Both populations made longer and more frequent feeding bouts inside the patch. Egg production measurements were in accordance with the behaviour of the laboratory population if no diel feeding rhythm was assumed. The field population produced fewer eggs than predicted from activity measurements, probably due to a diel feeding rhythm. It is concluded that laboratory reared A. tonsa can be used for experiments involving behaviour, but that the possible loss of diel rhythms should be a concern. Both populations differed considerably from field-caught A. tonsa from the eastern United States, where both behaviour and egg production changed consistently and in accordance with a strong aggregation in food patches. © 199

Are the plankton within the mixed layer homogeneously distributed? Implications for bloom-forming theories

Aquatic Sciences Meeting, Aquatic Sciences: Global And Regional Perspectives - North Meets South, 22-27 February 2015, Granada, SpainIntensive sampling in coastal waters of the central Red Sea during a period of thermal stratification showed that vertical patches of prokaryotes and nano- and microplankton developed and persisted for at least a week within the apparently well mixed layer. This vertical structure was most likely the result of in situ growth and mortality (e.g., grazing) rather than physical or behavioral aggregation. Adding nutrient-rich deep water simulating a mixing event triggered dense phytoplankton blooms in this nutrient-poor environment. These findings have implications for present bloom-forming theories because suggest that vertical structure within the mixed layer provides a critical seed mass that can rapidly exploit nutrient influx during early seasonal mixing.Peer Reviewe