Continuous Plankton Recorder Samples Research Articles

Mapping Selected Emergent Marine Toxin-Producing Organisms Using Historical Samples with Two Methods (Biosensors and Real-Time PCR): A Comparison of Resolution

The Continuous Plankton Recorder (CPR) survey is a valuable resource for mapping changes in plankton distribution and understanding harmful algal ecology because of its breadth and longevity. Preservation methods with formalin degrade DNA, making it difficult to use as a molecular tool for archived marine samples. DNA was extracted from CPR samples immediately after collection, seven months later and after nine years of storage from a cruise track along the Iberian Peninsula. PCR reactions performed from the nine-year timepoint were hybridized to probes in an electrochemical biosensor and compared to results obtained from RT-PCR performed at two earlier time points. The successful identification of Pseudo-nitzschia spp., Prorocentrum lima, Alexandrium minutum, Alexandrium ostenfeldii, Gambierdiscus spp. and Coolia spp. was documented. The biosensor analysis outperformed RT-PCR, allowing us to document certain tropical toxic dinoflagellates, viz., Gambierdiscus and Coolia, that produce human ciguatoxins and Coolia toxins, respectively. These non-native algal toxins can accumulate, pervade the food web and negatively impact human food security. This supports the northerly movement of microalgae with climate change in offshore Iberian peninsular waters. This study highlights biosensors as a cost-effective tool for the offshore monitoring of HAB species and advances molecular technologies for long-term CPR datasets that have limited records of harmful algae. DNA from formalin-preserved CPR samples is degraded, so the use of a short, multiprobe biosensor can augment historical plankton records with contemporary methods that also capture infrequently occurring benthic taxa carried in surface waters. The integration of probe-based biosensor technologies offers a promising avenue for exploring plankton dynamics in response to environmental changes.

Historical biomonitoring of pollution trends in the North Pacific using archived samples from the Continuous Plankton Recorder Survey

First started in 1931, the Continuous Plankton Recorder (CPR) Survey is the longest-running and most geographically extensive marine plankton sampling program in the world. This pilot study investigates the feasibility of biomonitoring the spatiotemporal trends of marine pollution using archived CPR samples from the North Pacific. We selected specimens collected from three different locations (British Columbia Shelf, Northern Gulf of Alaska, and Aleutian Shelf) in the North Pacific between 2002 and 2020. Comprehensive profiling of the plankton chemical exposome was conducted using liquid and gas chromatography coupled with tandem mass spectrometry (LC-MS/MS and GC–MS/MS). Our results show that phthalates, plasticizers, persistent organic pollutants (POPs), pesticides, pharmaceuticals, and personal care products were present in the plankton exposome, and that many of these pollutants have decreased in amount over the last two decades, which was most pronounced for tri-n-butyl phosphate. In addition, the plankton exposome differed significantly by regional human activities, with the most polluted samples coming from the nearshore area. Exposome-wide association analysis revealed that bioaccumulation of environmental pollutants was highly correlated with the biomass of different plankton taxa. Overall, this study demonstrates that exposomic analysis of archived samples from the CPR Survey is effective for long-term biomonitoring of the spatial and temporal trends of environmental pollutants in the marine environment.

Plankton monitoring in the Northwest Atlantic: a comparison of zooplankton abundance estimates from vertical net tows and Continuous Plankton Recorder sampling on the Scotian and Newfoundland shelves, 1999–2015

Abstract Assessment of zooplankton abundance, distribution, community composition, and temporal variability is critical to understanding the effects of climate variability and change on lower trophic level production and availability for consumption by larger consumers. Zooplankton sampling is performed across the Canadian continental shelf system by Fisheries and Oceans Canada's Atlantic Zone Monitoring Programme (AZMP). Sampling includes semi-monthly to monthly collection of zooplankton using vertical net tows (VNTs) deployed from near-bottom to surface at stations on the central Scotian Shelf (Stn 2, 150 m depth) and Newfoundland Shelf (Stn 27, 175 m depth), and by Continuous Plankton Recorders (CPRs) in the near-surface layers along routes over the Scotian and Newfoundland shelves (0–10 m depth). Here, we compare abundance metrics for 11 copepod taxa collected using both gear types in both regions between 1999 and 2015. Seasonal cycles of VNT and CPR abundance were similar for near-surface residents. VNT: CPR abundance ratios varied year-round for vertical migrants, as ontogenetic migrants shifted their vertical distribution, and as diel migrants changed their migratory behaviour. For some taxa, differences in annual average VNT: CPR abundance ratios between regions suggest differences in vertical distribution, while for others differences in inter-annual variability for VNT and CPR abundances suggest differences in the dynamics of the near- and sub-surface components of the populations.

Zooplankton communities along a Southern Ocean monitoring transect at 110° E from three CPR surveys (Dec 2014, Jan 2015, Mar 2015)

Many studies using surface plankton data from the Continuous Plankton Recorder (CPR) have suggested that micro- and meso-sized zooplankton species/taxa can serve as indicators of environmental change. But while regular CPR sampling would allow for the detection of changes in zooplankton communities, few intra-annual CPR surveys have been undertaken along single transects. We report the temporal variability of zooplankton community structure using CPR data collected along the Japanese monitoring transect (110° E) in December 2014, January 2015, and March 2015. We found zooplankton abundances in both the Polar Frontal Zone (PFZ) and Antarctic Zone (AZ) to increase from December to January, and mean AZ abundance to peak abruptly in January (381.9 ind. m−3) before decreasing to about 25% of that value in March. We attribute changes in total zooplankton abundance to fluctuations in the numbers of the two small dominant copepods, Oithona similis and Ctenocalanus citer. High AZ phytoplankton concentrations in December likely increased surface food availability, influencing population growth, and/or the timing of copepod seasonal ascension. We recommend future CPR surveys include sampling with finer mesh for more accurate determination of abundances of small-sized zooplankton, to better understand the ramifications of climate change on Southern Ocean trophic structure.

Capturing open ocean biodiversity: Comparing environmental DNA metabarcoding to the continuous plankton recorder.

Environmental DNA (eDNA) metabarcoding is emerging as a novel, objective tool for monitoring marine metazoan biodiversity. Zooplankton biodiversity in the vast open ocean is currently monitored through continuous plankton recorder (CPR) surveys, using ship-based bulk plankton sampling and morphological identification. We assessed whether eDNA metabarcoding (2L filtered seawater) could capture similar Southern Ocean zooplankton biodiversity as conventional CPR bulk sampling (~1,500L filtered seawater per CPR sample). We directly compared eDNA metabarcoding with (a) conventional morphological CPR sampling and (b) bulk DNA metabarcoding of CPR collected plankton (two transects for each comparison, 40 and 44 paired samples, respectively). A metazoan-targeted cytochrome c oxidase I (COI) marker was used to characterize species-level diversity. In the 2L seawater eDNA samples, this marker amplified large amounts of non-metazoan picoplanktonic algae, but eDNA metabarcoding still detected up to 1.6 times more zooplankton species than morphologically analysed bulk CPR samples. COI metabarcoding of bulk DNA samples mostly avoided nonmetazoan amplifications and recovered more zooplankton species than eDNA metabarcoding. However, eDNA metabarcoding detected roughly two thirds of metazoan species and identified similar taxa contributing to community differentiation across the subtropical front separating transects. We observed a diurnal pattern in eDNA data for copepods which perform diel vertical migrations, indicating a surprisingly short temporal eDNA signal. Compared to COI, a eukaryote-targeted 18S ribosomal RNA marker detected a higher proportion, but lower diversity, of metazoans in eDNA. With refinement and standardization of methodology, eDNA metabarcoding could become an efficient tool for monitoring open ocean biodiversity.

Lifeform indicators reveal large-scale shifts in plankton across the North-West European shelf.

Increasing direct human pressures on the marine environment, coupled with climate-driven changes, is a concern to marine ecosystems globally. This requires the development and monitoring of ecosystem indicators for effective management and adaptation planning. Plankton lifeforms (broad functional groups) are sensitive indicators of marine environmental change and can provide a simplified view of plankton biodiversity, building an understanding of change in lower trophic levels. Here, we visualize regional-scale multi-decadal trends in six key plankton lifeforms as well as their correlative relationships with sea surface temperature (SST). For the first time, we collate trends across multiple disparate surveys, comparing the spatially and temporally extensive Continuous Plankton Recorder (CPR) survey (offshore) with multiple long-term fixed station-based time-series (inshore) from around the UK coastline. These analyses of plankton lifeforms showed profound long-term changes, which were coherent across large spatial scales. For example, 'diatom' and 'meroplankton' lifeforms showed strong alignment between surveys and coherent regional-scale trends, with the 1998-2017 decadal average abundance of meroplankton being 2.3 times that of 1958-1967 for CPR samples in the North Sea. This major, shelf-wide increase in meroplankton correlated with increasing SSTs, and contrasted with a general decrease in holoplankton (dominated by small copepods), indicating a changing balance of benthic and pelagic fauna. Likewise, inshore-offshore gradients in dinoflagellate trends, with contemporary increases inshore contrasting with multi-decadal decreases offshore (approx. 75% lower decadal mean abundance), urgently require the identification of causal mechanisms. Our lifeform approach allows the collation of many different data types and time-series across the NW European shelf, providing a crucial evidence base for informing ecosystem-based management, and the development of regional adaptation plans.

Spatial and temporal patterns of Pseudo-nitzschia genetic diversity in the North Pacific Ocean from the Continuous Plankton Recorder survey

Several species of the marine diatom Pseudo-nitzschia can produce the neurotoxin domoic acid that is responsible for the seafood-borne illness amnesic shellfish poisoning in humans, marine wildlife mortalities and prolonged closures of fisheries resulting in economic losses to coastal communities. Since the year 2000, Pseudo-nitzschia species have been monitored in the Pacific Ocean with the Continuous Plankton Recorder (CPR). We used a combination of scanning electron microscopy with high-throughput and Sanger sequencing of CPR survey samples to compare the diversity of phytoplankton, including Pseudo-nitzschia species, from the north-eastern Pacific Ocean over 3 climatically different years: 2002, 2005 and 2008. A Pseudo-nitzschia-specific primer set targeting a partial region of the large subunit ribosomal DNA (rDNA) revealed spatially separated communities of Pseudo-nitzschia. The coastal region was dominated by a diverse array of P. fraudulenta unique sequences (operational taxonomic units), whereas the offshore region was rich in P. multiseries and contained a wide range of other Pseudo-nitzschia taxa, many not previously observed in this region. In 2008, exceptionally cold sea surface temperatures were recorded, influenced by a strong negative Pacific Decadal Oscillation signal. In that year, a more diverse assemblage of species was present in a spring open water sample, whereas P. fraudulenta was unusually rare from a coastal autumn sample. This is the first application of high-throughput genetic methods to uncover patterns of Pseudo-nitzschia genetic diversity from archival CPR samples, demonstrating the value of using CPR for plankton community analysis in rarely sampled regions of the oceans.

DdPCR applied on archived Continuous Plankton Recorder samples reveals long-term occurrence of class 1 integrons and a sulphonamide resistance gene in marine plankton communities.

Antibiotic resistance is a rising threat for human health. Although in clinical settings and terrestrial environments the rise of antibiotic resistant bacteria is well documented, their dissemination and spread in the marine environment, covering almost two-thirds of the Earth's surface, is still poorly understood. In this study, the presence and abundance of sulphonamide resistance gene (sul2) and class 1 integron-integrase gene (intI1), used as markers for the occurrence and spread of antibiotic resistance genes since the beginning of the antibiotic era, were investigated. Twenty-nine archived formalin-fixed samples, collected by the Continuous Plankton Recorder (CPR) survey in the Atlantic Ocean and North Sea from 1970 to 2011, were analysed using Droplet Digital PCR (ddPCR) applied for the first time on CPR samples. The two marker genes were present in a large fraction of the samples (48% for sul2 and 76% for intI1). In contrast, results from Real-Time PCR performed on the same samples greatly underestimate their occurrence (21% for sul2 and 52% for intI1). Overall, besides providing successful use of ddPCR for the molecular analysis of CPR samples, this study reveals long-term occurrence and spread of sul2 gene and class 1 integrons in the plankton-associated bacterial communities in the ocean.

Genetic monitoring of open ocean biodiversity: An evaluation of DNA metabarcoding for processing continuous plankton recorder samples.

DNA metabarcoding is an efficient method for measuring biodiversity, but the process of initiating long-term DNA-based monitoring programmes, or integrating with conventional programs, is only starting. In marine ecosystems, plankton surveys using the continuous plankton recorder (CPR) have characterized biodiversity along transects covering millions of kilometres with time-series spanning decades. We investigated the potential for use of metabarcoding in CPR surveys. Samples (n=53) were collected in two Southern Ocean transects and metazoans identified using standard microscopic methods and by high-throughput sequencing of a cytochrome c oxidase subunit I marker. DNA increased the number of metazoan species identified and provided high-resolution taxonomy of groups problematic in conventional surveys (e.g., larval echinoderms and hydrozoans). Metabarcoding also generally produced more detections than microscopy, but this sensitivity may make cross-contamination during sampling a problem. In some samples, the prevalence of DNA from large plankton such as krill masked the presence of smaller species. We investigated adding a fixed amount of exogenous DNA to samples as an internal control to allow determination of relative plankton biomass. Overall, the metabarcoding data represent a substantial shift in perspective, making direct integration into current long-term time-series challenging. We discuss a number of hurdles that exist for progressing DNA metabarcoding from the current snapshot studies to the requirements of a long-term monitoring programme. Given the power and continually increasing efficiency of metabarcoding, it is almost certain this approach will play an important role in future plankton monitoring.

Estimation of the Potential Detection of Diatom Assemblages Based on Ocean Color Radiance Anomalies in the North Sea

Over the past years, a large number of new approaches in the domain of ocean-color have been developed, leading to a variety of innovative descriptors for phytoplankton communities. One of these methods, named PHYSAT, currently allows for the qualitative detection of five main phytoplankton groups from ocean-color measurements. Even though PHYSAT products are widely used in various applications and projects, the approach is limited by the fact it identifies only dominant phytoplankton groups. This current limitation is due to the use of biomarker pigment ratios for establishing empirical relationships between \textit{in-situ} information and specific ocean-color radiance anomalies in open ocean waters. However, theoretical explanations of PHYSAT suggests that it could be possible to detect more than dominance cases but move more towards phytoplanktonic assemblage detection. Thus, to evaluate the potential of PHYSAT for the detection of phytoplankton assemblages, we took advantage of the Continuous Plankton Recorder (CPR) survey, collected in both the English Channel and the North Sea. The available CPR dataset contains information on diatom abundance in two large areas of the North Sea for the period 1998-2010. {Using this unique dataset, recurrent diatom assemblages were retrieved based on classification of CPR samples}. Six diatom assemblages were identified \textit{in-situ}, \textcolor{blue}{each having indicators taxa or species}. Once this first step was completed, the \textit{in-situ} analysis was used to empirically associate the diatom assemblages with specific PHYSAT spectral anomalies. This step was facilitated by the use of previous classifications of regional radiance anomalies in terms of shape and amplitude, coupled with phenological tools. Through a matchup exercise, three CPR assemblages were associated \textcolor{blue}{with} specific radiance anomalies. The maps of detection of these specific radiances anomalies are in close agreement with current \textit{in-situ} ecological knowledge.

Northerly shift of warm-water copepods in the western subarctic North Pacific: Continuous Plankton Recorder samples (2001-2013)

Spatial and temporal variation in copepod community structure, abundance, distribution and biodiversity were examined in the western subarctic North Pacific (40–53°N, 144–173°E) during 2001–2013. Continuous Plankton Recorder (CPR) observational data during the summer season (June and July) were analyzed. The latitudinal distribution of warm-water species in June shifted northward after 2011 while no apparent latitudinal shift of cold-water and other species was observed. Species number and the Shannon–Wiener biodiversity index (H′) in June tended to increase in the northern area after 2011. The warm-water species abundance and center latitude of warm-water distribution were positively correlated with sea surface temperature (SST) across sampling locations, whereas no significant correlations with SST were observed for cold-water species or other species. Warm SSTs in June after 2011 appeared to cause the northward shift of warm-water species distribution, which in turn contributed to the higher biodiversity in the northern area. This study demonstrated the rapid response of warm-water species to warm SST variation, whereas cold-water and other species did not exhibit such clear responses. These findings indicate that the response of copepods to environmental changes differs among copepod species, highlighting the importance of investigating lower trophic levels to the species level to evaluate individual species’ responses to climate change.

Comparative productivity and biomass yields of the Guinea Current LME

Plankton production patterns in the Guinea Current Large Marine Ecosystem (GCLME) were investigated using data obtained from Continuous Plankton Recorder (CPR) tows carried out in the GLCME, from December 1995 to November 1999. Four CPR routes were established between Cote d'Ivoire and Cameroon as part of the pilot phase of the GCLME project, funded by the Global Environment Facility. Phytoplankton and zooplankton yields were greatest during the major upwelling compared to the other identifiable hydrographic seasons. The phytoplankton was dominated by diatoms whereas smaller zooplankton (<2mm) occurred in greatest abundance. Analyses of ten years sea surface temperature (SST) data from 1990 to 2000 revealed two thermal regimes; a warmer phase followed by a colder phase that commenced in 1997. Annual phytoplankton and zooplankton yields in 1997 were relatively higher than the other years of the CPR sampling. Analyses of zooplankton community structure, in terms of species occurrence and relative abundances, was found to be similar during the minor and major upwelling. The zooplankton taxa contributing to dissimilarity in community structure were Chaetognath (<2mm), Oithona spp., Oncaea spp, copepod nauplii, echinoderm larvae, Para-Pseudocalanus, Temora spp., Eucalanus spp., and Clausocalanus spp. Spatial and seasonal variation in phytoplankton communities did not follow any pattern. It was observed from a multiple regression analysis that phytoplankton distribution alone accounted for a significant proportion of the variation in zooplankton distribution in all hydrographic seasons except the major upwelling, during which period sea surface temperature contributed over 60% of the observed variation. This investigation using CPR is the first of its kind in the GCLME and thus provides a baseline information to guide future studies.

GbpA as a Novel qPCR Target for the Species-Specific Detection of Vibrio cholerae O1, O139, Non-O1/Non-O139 in Environmental, Stool, and Historical Continuous Plankton Recorder Samples.

The Vibrio cholerae N-acetyl glucosamine-binding protein A (GbpA) is a chitin-binding protein involved in V. cholerae attachment to environmental chitin surfaces and human intestinal cells. We previously investigated the distribution and genetic variations of gbpA in a large collection of V. cholerae strains and found that the gene is consistently present and highly conserved in this species. Primers and probe were designed from the gbpA sequence of V. cholerae and a new Taq-based qPCR protocol was developed for diagnostic detection and quantification of the bacterium in environmental and stool samples. In addition, the positions of primers targeting the gbpA gene region were selected to obtain a short amplified fragment of 206 bp and the protocol was optimized for the analysis of formalin-fixed samples, such as historical Continuous Plankton Recorder (CPR) samples. Overall, the method is sensitive (50 gene copies), highly specific for V. cholerae and failed to amplify strains of the closely-related species Vibrio mimicus. The sensitivity of the assay applied to environmental and stool samples spiked with V. cholerae ATCC 39315 was comparable to that of pure cultures and was of 102 genomic units/l for drinking and seawater samples, 101 genomic units/g for sediment and 102 genomic units/g for bivalve and stool samples. The method also performs well when tested on artificially formalin-fixed and degraded genomic samples and was able to amplify V. cholerae DNA in historical CPR samples, the earliest of which date back to August 1966. The detection of V. cholerae in CPR samples collected in cholera endemic areas such as the Benguela Current Large Marine Ecosystem (BCLME) is of particular significance and represents a proof of concept for the possible use of the CPR technology and the developed qPCR assay in cholera studies.

A 60-year ocean colour data set from the continuous plankton recorder

The phytoplankton colour index (PCI) of the Continuous Plankton Recorder (CPR) survey is an in situ measure of ocean colour, which is considered a proxy of the phytoplankton biomass. PCI has been extensively used to describe the major spatiotemporal patterns of phytoplankton in the North Atlantic Ocean and North Sea since 1931. Regardless of its wide application, the lack of an adequate evaluation to test the PCI's quantitative nature is an important limitation. To address this concern, a field trial over the main production season has been undertaken to assess the numerical values assigned by previous investigations for each category of the greenness of the PCI. CPRs were towed across the English Channel from Roscoff to Plymouth consecutively for each of 8 months producing 76 standard CPR samples, each representing 10 nautical miles of tow. The results of this experiment test and update the PCI methodology, and confirm the validity of this long-term in situ ocean colour data set. In addition, using a 60-year time series of the PCI of the western English Channel, a comparison is made between the previous and the current revised experimental calculations of PCI.

Copepod distribution in surface waters of the Drake Passage using Continuous Plankton Recorder and a Pump-Net onboard system

There is no single instrument that can sample quantitatively the complete spectrum of pelagic organisms, or even all the components of zooplankton. Mesh size is the main factor affecting species selectivity in the Continuous Plankton Recorder (CPR), implying a need to use multiple net systems to fully characterize a community. The spatial distribution of copepod communities in the water masses of the western and eastern sectors of Drake Passage were studied using, respectively, a CPR and a Pump Net onboard system. For this purpose, and assuming that copepod community size structures of each of the three water masses were similar in both the sectors studied, the possibility of complementing CPR results using a Pump-Net onboard system was evaluated. The latter system allows the estimation of absolute abundances and has the advantage of solving two problems associated with CPR, namely mesh clogging and low catching efficiency. The contribution of the nauplius forms and species accurately identified with both samplers was analyzed. Although Oithona similis dominated both communities, in the western sector small species made a greater contribution than Calanus simillimus, the opposite being true for the eastern sector. Nauplii and early copepodite stages of O. similis were missing from the CPR samples and represented between 69 and 79% of total copepod communities, whereas small calanoid copepods, C. simillimus copepodites and later stages of O. similis were inaccurately sampled by the CPR and represented between 14 and 18% of the copepod community. Hence, the Pump Net sampler is useful for complementing the semi-quantitative information of the CPR and for its calibration.

Monitoring changes in phytoplankton abundance and composition in the Northwest Atlantic: a comparison of results obtained by continuous plankton recorder sampling and colour satellite imagery

Phytoplankton abundance in the NW Atlantic was measured by continuous plankton recorder (CPR) sampling along tracks between Iceland and the western Scotian Shelf from 1998 to 2006, when sea-surface chlorophyll (SSChl) measurements were also being made by ocean colour satellite imagery using the SeaWiFS sensor. Seasonal and inter-annual changes in phytoplankton abundance were examined using data collected by both techniques, averaged over each of four shelf regions and four deep ocean regions. CPR sampling had gaps (missing months) in all regions and in the four deep ocean regions satellite observations were too sparse between November and February to be of use. Average seasonal cycles of SSChl were similar to those of total diatom abundance in seven regions, to those of the phytoplankton colour index in six regions, but were not similar to those of total dinoflagellate abundance anywhere. Large inter-annual changes in spring bloom dynamics were captured by both samplers in shelf regions. Changes in annual (or 8 months) averages of SSChl did not generally follow those of the CPR indices within regions and multi-year averages of SSChl, and the three CPR indices were generally higher in shelf than in deep ocean regions. Remote sensing and CPR sampling provide complementary ways of monitoring phytoplankton in the ocean: the former has superior temporal and spatial coverage and temporal resolution, and the latter provides better taxonomic information.

Spatial and inter-decadal variability in plankton abundance and composition in the Northwest Atlantic (1958–2006)

The results of Continuous Plankton Recorder sampling in the NW Atlantic between 1958 and 2006 are presented for 11 plankton taxa in eight shelf and deep ocean regions. For shelf regions, phytoplankton abundances increased in the early 1990s, mainly in winter, as the contribution of Arctic-derived freshwater to the Newfoundland (NLS) and Scotian shelves (SS) increased. Farther east, in the sub-polar gyre, phytoplankton levels increased with rising temperatures during the 1990s and 2000s. In both areas, the changes can be explained by increased stratification. The increased influx of arctic water to the NLS in the 1990s was also probably directly responsible for the increased abundances of two arctic Calanus species (C. glacialis and C. hyperboreus) and indirectly responsible for the decreased abundance of Calanus I–IV (mainly C. finmarchicus), perhaps via changes in food composition. On the SS the arctic Calanus species increased in abundance in the 2000s, likely as the result of increased transport from the Arctic via the Gulf of St Lawrence. In the deep ocean, plankton seasonal cycles changed little over the decades and increasing phytoplankton levels in the 2000s were accompanied by increases in zooplankton abundance, suggesting bottom-up control. In shelf regions, phytoplankton increases in the 1990s were in winter and Calanus I–IV appeared earlier in spring than in previous decades. Zooplankton levels generally did not change overall however, perhaps because the species examined were mainly inactive during winter.

A blooming jellyfish in the northeast Atlantic and Mediterranean

A long-term time series of plankton records collected by the continuous plankton recorder (CPR) Survey in the northeast Atlantic indicates an increased occurrence of Cnidaria since 2002. In the years 2007 and 2008, outbreaks of the warm-temperate scyphomedusa, Pelagia noctiluca, appeared in CPR samples between 45° N to 58° N and 1° W to 26° W. Knowing the biology of this species and its occurrence in the adjacent Mediterranean Sea, we suggest that P. noctiluca may be exploiting recent hydroclimatic changes in the northeast Atlantic to increase its extent and intensity of outbreaks. In pelagic ecosystems, Cnidaria can affect fish recruitment negatively. Since P. noctiluca is a highly venomous species, outbreaks can also be detrimental to aquaculture and make bathing waters unusable, thus having profound ecological and socio-economic consequences.

Identification of jellyfish from Continuous Plankton Recorder samples

Previous analysis of the Continuous Plankton Recorder (CPR) long-term data set for the presence of ‘coelenterate’ tissue revealed changes in the frequency of jellyfish occurrence in the North Atlantic Ocean and North Sea; however, the identities of the jellyfish were unknown, causing uncertainty in interpreting these findings. To improve the utility of the ‘coelenterate’ data from the CPR, 62 CPR samples were selected for re-analysis from an area where the widespread occurrence of the holoplanktonic scyphomedusan, Pelagia noctiluca (Forsskal, 1775), was previously documented from net tows to test if the CPR sampled P. noctiluca. Examination of the samples revealed smears (<1 mm) of golden gelatinous tissue on the sampling mesh. Subsequent microscopic examination and measurement of nematocysts identified most of the smears as P. noctiluca. Indeed, P. noctiluca was identified on 53% of the CPR samples from the area that best coincided with the documented bloom area. Although hydrozoans were also identified in the samples, the characteristic golden colour of P. noctiluca and its distinct suite of nematocysts allowed identification to species level. The identification of other jellyfish may be more complicated due to the labour-intensive examination of samples and unclear delineation of nematocyst types when multiple similar species are present. Nevertheless, re-analysis of CPR samples holds great promise for identifying the underlying reason for increases in jellyfish occurrence in the CPR records.

Shortened duration of the annual Neocalanus plumchrus biomass peak in the Northeast Pacific

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 393:189-198 (2009) - DOI: https://doi.org/10.3354/meps08044 Shortened duration of the annual Neocalanus plumchrus biomass peak in the Northeast Pacific Sonia D. Batten1,*, David L. Mackas2 1Sir Alister Hardy Foundation for Ocean Science, c/o 4737 Vista View Cr., Nanaimo, British Columbia V9V 1N8, Canada 2Fisheries and Oceans Canada, Institute of Ocean Sciences, PO Box 6000, Sidney, British Columbia V8L 4B2, Canada *Email: soba@sahfos.ac.uk ABSTRACT: The calanoid copepod Neocalanus plumchrus (Marukawa) is a dominant member of the spring mesozooplankton in the subarctic North Pacific and Bering Sea. Previous studies have shown interdecadal and latitudinal variation in seasonal developmental timing, with peak biomass occurring earlier in years and places with warmer upper ocean temperatures. Because N. plumchrus normally has a single dominant annual cohort, its seasonal timing can be indexed from measurements of total population biomass or by following progressive changes in stage composition. Early studies empirically found that peak upper ocean biomass occurred when about half of the pre-dormant population had reached copepodite stage 5 (C5). However, more recent comparisons derived from recent Continuous Plankton Recorder (CPR) data now show peak biomass when a larger fraction (>80%) of the population is at C5. CPR samples the surface 10 to 15 m, but comparisons to depth-resolved BIONESS data show that this discrepancy is not an artefact of sampling depth. Other causes are either a prolongation of duration of pre-dormant C5 or a narrowing of the age range making up the annual cohort. We assessed changes in cohort width using a modification of Greve’s cumulative percentile method, and found that average cohort widths in the Alaska Gyre were significantly narrower in 2000–2007 than in 1957–1965 (1968–1980 were intermediate). Net tow sampling of Strait of Georgia populations showed a similar significant narrowing of cohorts in the 2003–2005 sampling period. This study provides evidence that in addition to the shift to an earlier occurrence of peak biomass reported previously, the duration of the peak has also decreased in the last decade. KEY WORDS: Neocalanus plumchrus · Copepod · Biomass · Continuous Plankton Recorder Full text in pdf format PreviousNextCite this article as: Batten SD, Mackas DL (2009) Shortened duration of the annual Neocalanus plumchrus biomass peak in the Northeast Pacific. Mar Ecol Prog Ser 393:189-198. https://doi.org/10.3354/meps08044Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 393. Online publication date: October 30, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.