Jeffrey A. Runge

Marine plankton phenology and life history in a changing climate: current research and future directions

Increasing availability and extent of biological ocean time series (from both in situ and satellite data) have helped reveal significant phenological variability of marine plankton. The extent to which the range of this variability is modified as a result of climate change is of obvious importance. Here we summarize recent research results on phenology of both phytoplankton and zooplankton. We suggest directions to better quantify and monitor future plankton phenology shifts, including (i) examining the main mode of expected future changes (ecological shifts in timing and spatial distribution to accommodate fixed environmental niches vs. evolutionary adaptation of timing controls to maintain fixed biogeography and seasonality), (ii) broader understanding of phenology at the species and community level (e.g. for zooplankton beyond Calanus and for phytoplankton beyond chlorophyll), (iii) improving and diversifying statistical metrics for indexing timing and trophic synchrony and (iv) improved consideration of spatio-temporal scales and the Lagrangian nature of plankton assemblages to separate time from space changes.

On birth and death in the sea

We present the first comparative study of the stage-specific patterns of mortality of Calanus and Pseudocalanus, two widely distributed genera that are representative of a relatively large-bodied, broadcast spawning calanoid copepod and a relatively small-bodied, egg-brooding calanoid. The study site is Georges Bank, a continental shelf locality in the Northwestern Atlantic with retentive circulation that renders it suitable for studies of population dynamics. Based on extensive mortality estimates from 30 cruises, we find that co-occurring Calanus finmarchicus and Pseudocalanus spp. have markedly different patterns of stage-specific mortality, the former bimodal and the latter relatively uniform with respect to developmental stage. Neither taxon exhibits a monotonic decline in mortality with developmental stage, nor are rates of mortality predictable in a useful manner by copepod body size or by ambient temperature. Young stages of the broadcast-spawning C. finmarchicus show conditional density-dependence of mortality rates, i.e. mortality rates are independent of population density when adult females are low in abundance but positively related to population density at high female abundances. This density-dependence, which is probably attributable to egg cannibalism, introduces a quadratic mortality term into population dynamic models. The egg-brooding Pseudocalanus spp., in contrast, show no evidence of density-dependent mortality. The two taxa illustrate a life history trade-off: the broadcast-spawning Calanus exhibits birth rates that are greatly elevated with respect to those of Pseudocalanus, but there is a compensatory cost in very low survivorship of the freely spawned eggs. Both the high fecundity, high mortality life history of Calanus and the low fecundity, low mortality life history of Pseudocalanus appear to have approximately equal fitness in this study site.

Copepod production drives recruitment in a marine fish

Predicting fluctuations in recruitment of commercial marine fish remains the Holy Grail of fisheries science. In previous studies, we identified statistical relationships linking Atlantic mackerel ...

Fecundity characteristics of Calanus finmarchicus in coastal waters of eastern Canada

Abstract Results of an earlier study of fecundity characteristics of the copepod Calanus finmarchicus from the shelf off Nova Scotia are combined with more recent observations from the Estuary and Gulf of St. Lawrence, where female Calanus are considerably larger. Maximum egg production rates of Lower Estuary females in laboratory experiments were consistent with predictions based on the previously-derived relationship between maximum egg production rates and temperature, in which a culture of Thalassiosira weissflogii was used as the food source. Clutch sizes varied considerably and were significantly related to body size. Within a given body size, clutch sizes were observed to differ by up to a factor of two, possibly associated with differences in food availability or female age. Clutch size of Calanus finmarchicus may represent the interaction between the egg production rate that can be supported by the contemporaneous food conditions and the constraint imposed by the diel spawning cycle. Measurement ...

Advanced recruitment and accelerated population development in Arctic calanoid copepods of the North Water

Abstract The timing of copepodite recruitment and population development of copepods in spring and early summer (April–July) were compared between the North Water polynya and Barrow Strait, a non-polynya region in the Canadian Archipelago. In the North Water, young copepodites (CI–CIII) of calanoid herbivores were concentrated in the cold and chlorophyll-rich water at the base of the Arctic surface layer, while later stages (CIV–CV) invaded the warmer surface layer. The phytoplankton bloom and the recruitment of the first cohort of copepodites of Calanus hyperboreus , C. glacialis , and Pseudocalanus spp started in May–June, some 1.5–3 months earlier than in Barrow Strait. Consistent with a precocious summer recruitment, population stage structure of these species in early spring (April–May) was more advanced in the North Water than in Barrow Strait. The recruitment in June of CI of the omnivore Metridia longa was advanced by at least 5 weeks in the polynya relative to Barrow Strait. We found no evidence for an acceleration of the population development of the small Microcalanus pygmaeus , Oithona similis or Oncaea borealis in the polynya. Once the recruitment of young copepodites had started, recruitment success (i.e. % of young copepodites in the population) increased primarily with Chl a concentration for C. hyperboreus , with both sea-surface temperature and Chl a for C. glacialis , and with temperature only for Pseudocalanus spp. Hence, depending on the species, both greater food availability and higher temperature resulting from reduced ice cover contributed to improve reproductive success in herbivorous copepods in the North Water relative to Barrow Strait. A climate-induced reduction of ice cover duration is predicted to favour the population growth of the predominant large calanoid copepods and Pseudocalanus on Arctic shelves.

Voracious planktonic hydroids: unexpected predatory impact on a coastal marine ecosystem

Abstract-Hydroids are typically attached, benthic cnidarians that feed on a variety of small prey. During sampling on Georges Bank in spring 1994, we found huge numbers of hydroids suspended in the plankton. They fed on young stages of copepods that are an important prey for fish, as well as on young fish themselves. Two independent methods were used to estimate feeding rates of the hydroids; both indicate that the hydroids are capable of consuming from 50% to over 100% of the daily production of young copepods. These results suggest that hydroids can have a profound effect on the population dynamics of zooplankton and young fish on Georges Bank. Copyright 0 1996 Elsevier Science Ltd INTRODUCTION The life history of marine hydrozoans (Phylum Cnidaria) is typically an alternation between a sessile hydroid phase and a motile medusa. The hydroids form colonies attached to seaweed, rocks or other organisms, and their feeding polyps (hydranths) prey on small organisms, eggs and detrital matter. The medusae are usually released to feed and disperse in the plankton (Hyman, 1940). We report observations from Georges Bank on the occurrence of suspended colony fragments of the hydroid

Evaluating the synopticity of the US GLOBEC Georges Bank broad-scale sampling pattern with observational system simulation experiments ☆

Abstract A set of observational system simulation experiments (OSSEs) have been designed to assess quantitatively the synopticity of the broad-scale surveys of Georges Bank carried out as part of the US GLOBEC program. The approach uses model simulations that contain realistic spatial and temporal fluctuations of adult females of the planktonic copepod Calanus finmarchicus observed during February and March 1995. Simulations are constructed with two types of assimilation procedures (nudging and the adjoint method), which are used to dynamically interpolate between the two broad-scale surveys taken one month apart. Using these simulations as representations of the real ocean, the model fields are subsampled in space and time along a typical cruise track. These simulated data are then objectively analyzed and the resulting maps compared with “reality” as represented in the original simulation. Results indicate a total error of approximately 50%, which is comprised mostly of simple mapping error (incomplete spatial sampling) and a smaller contribution from space/time smearing. Adjustment of the station positions for displacement by the mean flow reduces the latter error by about half.

Early life stages of the Arctic copepod Calanus glacialis are unaffected by increased seawater pCO2

&NA; As the worlds oceans continue to absorb anthropogenic CO2 from the atmosphere, the carbonate chemistry of seawater will change. This process, termed ocean acidification, may affect the physiology of marine organisms. Arctic seas are expected to experience the greatest decreases in pH in the future, as changing sea ice dynamics and naturally cold, brackish water, will accelerate ocean acidification. In this study, we investigated the effect of increased pCO2 on the early developmental stages of the key Arctic copepod Calanus glacialis. Eggs from wild‐caught C. glacialis females from Svalbard, Norway (80°N), were cultured for 2 months to copepodite stage C1 in 2°C seawater under four pCO2 treatments (320, 530, 800, and 1700 &mgr;atm). Developmental rate, dry weight, and carbon and nitrogen mass were measured every other day throughout the experiment, and oxygen consumption rate was measured at stages N3, N6, and C1. All endpoints were unaffected by pCO2 levels projected for the year 2300. These results indicate that naupliar development in wild populations of C. glacialis is unlikely to be detrimentally affected in a future high CO2 ocean.

Regulation of gene expression is associated with tolerance of the Arctic copepod Calanus glacialis to CO2-acidified sea water

Abstract Ocean acidification is the increase in seawater pCO 2 due to the uptake of atmospheric anthropogenic CO 2, with the largest changes predicted to occur in the Arctic seas. For some marine organisms, this change in pCO 2, and associated decrease in pH, represents a climate change‐related stressor. In this study, we investigated the gene expression patterns of nauplii of the Arctic copepod Calanus glacialis cultured at low pH levels. We have previously shown that organismal‐level performance (development, growth, respiration) of C. glacialis nauplii is unaffected by low pH. Here, we investigated the molecular‐level response to lowered pH in order to elucidate the physiological processes involved in this tolerance. Nauplii from wild‐caught C. glacialis were cultured at four pH levels (8.05, 7.9, 7.7, 7.5). At stage N6, mRNA was extracted and sequenced using RNA‐seq. The physiological functionality of the proteins identified was categorized using Gene Ontology and KEGG pathways. We found that the expression of 151 contigs varied significantly with pH on a continuous scale (93% downregulated with decreasing pH). Gene set enrichment analysis revealed that, of the processes downregulated, many were components of the universal cellular stress response, including DNA repair, redox regulation, protein folding, and proteolysis. Sodium:proton antiporters were among the processes significantly upregulated, indicating that these ion pumps were involved in maintaining cellular pH homeostasis. C. glacialis significantly alters its gene expression at low pH, although they maintain normal larval development. Understanding what confers tolerance to some species will support our ability to predict the effects of future ocean acidification on marine organisms.

Coastal amplification of supply and transport (CAST): a new hypothesis about the persistence of Calanus finmarchicus in the Gulf of Maine

hypothesis about the persistence of Calanus finmarchicus in the Gulf of Maine Rubao Ji*, Zhixuan Feng, Benjamin T. Jones, Cameron Thompson, Changsheng Chen, Nicholas R. Record, and Jeffrey A. Runge Department of Biology, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA School of Marine Sciences, University of Maine and Gulf of Maine Research Institute, Portland, ME, USA School for Marine Science and Technology, University of Massachusetts Dartmouth, Dartmouth, MA, USA Bigelow Laboratory for Ocean Sciences, 60 Bigelow Dr, East Boothbay, ME 04544, USA