Marine Zooplankton Research Articles

Copepod abundance distribution in relation to a cyclonic eddy in a coastal environment in the southern Gulf of California

Marine zooplankton play a pivotal position in the pelagic ecosystem and, as one of their principal members, copepods represent by far the most significant direct link between phytoplankton and the higher trophic levels. In this study, observational evidence of the effect of a mesoscale cyclonic eddy on the abundance of copepods (adult calanoids, adult cyclopoids and all copepodite stages) in the Bay of La Paz, southern Gulf of California, a region recognized as exhibiting high biodiversity, is presented. During a multidisciplinary research cruise in February 2006, high-resolution hydrographic profiles were obtained from a grid of stations throughout the bay, and oblique zooplankton hauls were made in its north-central portion. The results showed the presence of a mature mesoscale cyclonic eddy, which extended to 110 m depth and 30 km diameter, reaching a surface azimuthal velocity of 20 cm s–1 at its periphery. Below the mixed layer at 50 m depth this eddy induced a cold-core water dome (~16.25 °C) at its center. Within this cold water dome, nutrients concentrations were much higher than outside the eddy. Nitrate reached up to 15 μM, soluble reactive phosphorous (SRP) up to 1.6 μM, and soluble reactive silicate (SRSi) up to 30 μM within the eddy. The total abundance of the organisms analyzed varied according to group: the calanoid copepods reached values of 8112 ind 100 m–3, the cyclopoid copepods of 4281 ind 100 m–3, and the highest abundance was recorded by all copepodite stages, of 32,076 ind 100 m–3. The influence of the cyclonic structure on copepod abundance was to induce the formation of a circular shape around the eddy periphery, which could be called a ‘copepod belt shape’. We suggest that several mechanisms induce this aggregation, including: 1) the affinity of these organisms for waters with a favorable temperature, and 2) the availability of food (phytoplankton) generated by the presence of the cyclonic eddy and the sub-mesoscale processes there, as well as by the presence of a bathymetric sill. These results represent the first observational report on the influence of a mesoscale cyclonic eddy in the Bay of La Paz on zooplankton organisms in winter, which should contribute to a better understanding of the dynamics of this highly productive area.

Microplastics as vectors of metals contamination in Mediterranean Sea.

Microplastics are contaminants of great concern all over the world. Microplastics constitute pollutants themselves; moreover, other contaminants such as metals are easily absorbed on their plastic surface, becoming bioavailable to marine biota such as zooplankton.We collected marine zooplankton from Mediterranean Sea to investigate trace elements associated with microplastics. Samples were subjected to visual sorting by a stereomicroscope, collected with sterile tweezers, pooled and subjected to sonication, filtration, and drying before being subjected to acid extraction. An ICP-MS was utilized for multi-elemental determination.Aluminum, iron, chromium, zinc, nickel, molybdenum, manganese, lead cobalt, and copper were found at concentrations of mg/kg while arsenic, vanadium, rubidium, and cadmium at level of μg kg-1. Other elements such as silver, beryllium, bismuth, selenium, tin, and thallium were under the limit of quantitation. Lower levels of iron and manganese in samples from Italy were found in comparison to England and Brazil, while aluminum, copper, and zinc registered comparable values. The presence of metals in marine waters is strictly related to sediment lithology and anthropogenic inputs, but plastic plays a key role as vectors for metal ions in the marine system, being able to concentrate metals several order of magnitude higher than in surrounding waters and exerting potential toxicity for living beings after chronic exposure.

Effects of polystyrene in the brackish water flea Diaphanosoma celebensis: Size-dependent acute toxicity, ingestion, egestion, and antioxidant response.

Owing to the increasing usage of plastics, their debris is continuously deposited in marine environments, resulting in deleterious effects on aquatic organisms. Although it is known that microplastics disturb the cellular redox status, knowledge of molecular in marine cladocerans is still lacking. In the present study, we investigated the acute toxicity of different-sized polystyrene (PS) beads (0.05, 0.5, and 6-μm diameter), ingestion and egestion patterns, their distribution in the tissues, and their effects on the antioxidant systems in the brackish water flea Diaphanosoma celebensis. All different-sized PS beads showed no mortality at the concentrations used in this study. After 48 h of exposure to PS beads of different sizes, all microbeads were retained in the digestive tract, but the retention time varied according to the bead size. In particular, the group that was exposed to 0.05-μm beads showed widely distributed fluorescence (e.g., in the embryo, and probably in lipid droplets as well as the digestive tract). The transcriptional level and enzyme activities of antioxidants were modulated depending on the size of the PS beads, and lipid peroxidation was induced in groups exposed to 0.05 and 0.5-μm beads. These findings suggest that the size of PS beads is an important factor for cellular toxicity, and can induce size-dependent oxidative stress in this species. This study provides a better understanding of the molecular modes of action of microplastics in marine zooplankton.

H3S28PAntibody Stainingof Okinawan Oikopleura dioicaSuggests the Presence of Three Chromosomes.

Oikopleura dioica is a ubiquitous marine zooplankton of biological interest owing to features that include dioecious reproduction, a short life cycle, conserved chordate body plan, and a compact genome. It is an important tunicate model for evolutionary and developmental research, as well as investigations into marine ecosystems. The genome of north Atlantic O. dioica comprises three chromosomes. However, comparisons with the genomes of O. dioica sampled from mainland and southern Japan revealed extensive sequence differences. Moreover, historical studies have reported widely varying chromosome counts. We recently initiated a project to study the genomes of O. dioicaindividuals collected from the coastline of the Ryukyu (Okinawa) Islands in southern Japan. Given the potentially large extent of genomic diversity, we employed karyological techniques to count individual animals' chromosomes in situ using centromere-specific antibodies directed against H3S28P, a prophase-metaphase cell cycle-specific marker of histone H3. Epifluorescence and confocal images were obtained of embryos and oocytes stained with two commercial anti-H3S28P antibodies (Abcam ab10543 and Thermo Fisher 07-145). The data lead us to conclude that diploid cells from Okinawan O. dioicacontain three pairs of chromosomes, in line with the north Atlantic populations. The finding facilitates the telomere-to-telomere assembly of Okinawan O. dioica genome sequences and gives insight into the genomic diversity of O. dioica from different geographical locations. The data deposited in the EBI BioImage Archive provide representative images of the antibodies' staining properties for use in epifluorescent and confocal based fluorescent microscopy.

Metabarcoding reveals hidden species and improves identification of marine zooplankton communities in the North Sea

Abstract Although easily collected in large numbers, the subsequent processing and identification of zooplankton have usually been a barrier to large-scale biodiversity assessments. Therefore, DNA barcoding has been increasingly used by non-taxonomists to identify specimens. Here, we studied the community composition of zooplankton in the Belgian part of the North Sea over the course of 1 year. We identified zooplankton using both a traditional approach based on morphological characteristics and by metabarcoding of a 650 bp fragment of the V4-V5 region of the 18S rRNA gene using nanopore sequencing. Using long rDNA sequences, we were able to identify several taxa at the species level, across a broad taxonomic scale. Using both methods, we compared community composition and obtained diversity metrics. Diversity indices were not significantly correlated. Metabarcoding allowed for comparisons of diversity and community composition, but not all groups were successfully sequenced. Additionally, some disparities existed between relative abundances of the most abundant taxa based on traditional counts and those based on sequence reads. Overall, we conclude that for zooplankton samples, metabarcoding is capable of detecting taxa with a higher resolution, regardless of developmental stage of the organism. Combination of molecular and morphological methods results in the highest detection and identification levels of zooplankton.

Winter zooplankton dynamics in the English Channel and southern North Sea: trends and drivers from 1991 to 2013

Abstract Winter has long been regarded as a period of minor importance in marine zooplankton ecology with static, low concentrations and growth rates of organisms. Yet, there is growing evidence that winter conditions influence spring bloom strength. With rising water temperatures, growing importance of fish larvae survival during winter and the lack of data to parameterize ecosystem models for this period, research focus shifted on winter zooplankton ecology. To enable looking into past changes in winter zooplankton ecology, we established a new winter zooplankton time series based on samples collected in the eastern English Channel and southern North Sea by the International Herring Larvae Survey since 1988. Four areas of the study region were identified containing different congregations of zooplankton. Overall, zooplankton size decreased while total zooplankton abundance increased, reaching its maximum in 2011. Zooplankton abundance dynamics were mainly related to temperature, chlorophyll a concentration and North Atlantic Oscillation index. Depth and Atlantic water inflow strongly influenced zooplankton size. Increased chlorophyll a concentration and high abundances of small copepods indicated bottom-up controlled secondary production since 2010 and a possible winter bloom in 2011. Based on the analysed parameters, no relation between herring larvae abundance and zooplankton or environmental drivers was determined.

A marine zooplankton community vertically structured by light across diel to interannual timescales.

The predation risk of many aquatic taxa is dominated by visually searching predators, commonly a function of ambient light. Several studies propose that changes in visual predation will become a major climate-change impact on polar marine ecosystems. The High Arctic experiences extreme seasonality in the light environment, from 24 h light to 24 h darkness, and therefore provides a natural laboratory for studying light and predation risk over diel to seasonal timescales. Here, we show that zooplankton (observed using acoustics) in an Arctic fjord position themselves vertically in relation to light. A single isolume (depth-varying line of constant light intensity, the value of which is set at the lower limit of photobehaviour reponses of Calanus spp. and krill) forms a ceiling on zooplankton distribution. The vertical distribution is structured by light across timescales, from the deepening of zooplankton populations at midday as the sun rises in spring, to the depth to which zooplankton ascend to feed during diel vertical migration. These results suggest that zooplankton might already follow a foraging strategy that will keep visual predation risk roughly constant under changing light conditions, such as those caused by the reduction of sea ice, but likely with energetic costs such as lost feeding opportunities as a result of altered habitat use.

Molecular-based approach for revealing community struc ture and diversity of marine zooplankton

Molecular-based approach for revealing community struc ture and diversity of marine zooplankton

Metabarcoding of zooplankton diversity within the Chukchi Borderland, Arctic Ocean: improved resolution from multi-gene markers and region-specific DNA databases

DNA-based analyses have become powerful tools for characterizing the metazoan biodiversity of diverse marine ecosystems. Metabarcoding (i.e., large-scale taxonomic identification of complex samples via high-throughput sequencing of a DNA barcode region) frequently uses hypervariable regions of the nuclear eukaryotic 18S ribosomal RNA (rRNA) gene. However, species-level taxonomic identification is hampered by the conservative nature of the 18S gene in comparison to the mitochondrial cytochrome oxidase I (COI) barcode gene. Additionally, metabarcoding relies on reference DNA sequence databases for classification of millions of unknown sequence reads and molecular operational taxonomic units (OTUs); databases that are at present depauperate for marine zooplankton taxa. Here, we characterized the mesozooplankton community for the Chukchi Borderland (CBL) region, western Arctic Ocean, through metabarcoding analysis of the V4 and V9 hypervariable regions of 18S rRNA and a portion of COI. Characterization of zooplankton diversity for the epipelagic and upper mesopelagic layers (0–500 m) was based upon 17 metazoan taxonomic categories encompassing 24 orders in 14 classes. Taxonomic classification using the V4 and V9 markers was most reliable for orders, with copepods dominating OTU counts. To increase taxonomic resolution and allow detection of species, V4, V9, and COI OTUs were classified against DNA sequence databases for the Arctic Ocean for the subclass Copepoda. The geographic region-specific databases for 18S rRNA and COI resulted in the detection and identification of 6 genera and 49 species of copepods representing 23 families, a marked increase in the taxonomic classification of the 18S rRNA markers. The greatest copepod species diversity was captured with V4 (34 species) followed by COI (28 species) with the least copepod diversity detected by V9 (5 species). Our results demonstrate the power of using multiple gene markers, with DNA reference databases that are specific to the geographic region of interest, providing more accurate metabarcoding biodiversity measures for the copepod assemblages compared to universal metazoan sequence reference databases. Results from this study highlight the need for continued DNA barcode sequencing to increase species representation in the reference sequence databases that are crucial for accurate characterization of mesozooplankton communities.

Zooplankton abundance during summer in the Bay of La Paz (southwestern Gulf of California, Mexico)

Marine zooplankton play key roles in the transfer of energy to higher trophic levels and the removal of CO2 from the atmosphere through the sedimentation of inorganic and organic carbon compounds included in their fecal pellets. Therefore, differences in the zooplankton groups driven by climate variations could influence the biogeochemical cycles at large oceanic scales. As a contribution to this topic, we analyzed the zooplankton groups in the Bay of La Paz, Gulf of California, Mexico, a highly dynamic basin characterized by its high biological productivity. We used information gathered during multidisciplinary research cruises in the summers of 2008 and 2009. The results showed differences in the hydrographic parameters between both summers, with a higher temperature recorded in 2009. The zooplankton groups showed that the calanoid copepods were the most abundant; however, there were important differences in the relative abundance of the rest of the analyzed groups as an effect of the temperature distribution along the study area, which was confirmed by multivariate statistical methods. These temperature changes were associated with increased gelatinous zooplankton (Cnidaria, Chaetognatha, Appendicularia, and Ctenophora) in 2009 in a region where the temperature was higher, possibly as a result of changes in food (phytoplankton) availability.

The gut retention time of microplastics in barnacle naupliar larvae from different climatic zones and marine habitats.

Microplastic ingestion has been widely documented in marine zooplankton, but the retention time of microplastics in their digestive gut are still poorly studied, especially among species from different climatic zones and marine habitats. This study evaluated the ingestion and gut retention time of four sizes of fluorescent microplastic beads (1.3, 7.3, 10.6, and 19.0μm) in stage II naupliar larvae of nine barnacle species from different habitats (epibiotic on turtles, mangroves, coral reefs, and rocky shores) and climatic zones (subtropical/tropical and temperate). Microbeads were not lethal to all species (climatic zones/habitats) tested from the four sizes of non-fluorescent virgin microbeads (1.7, 6.8, 10.4 and 19.0μm, each at concentrations 1, 10, 100, and 1000 beads mL-1). Gut retention time of microplastic beads in barnacle naupliar larvae significantly increased with decreasing size. Microbeads resided in digestive tracts generally 3-4 times longer in rocky shore and coral reef barnacles than in muddy shore and epibiotic ones. However, species from different climatic zone did not differ in retention time. Our results suggested nauplius larvae from rocky shore and coral reef barnacles appear to be more susceptible to the impacts of longer retained microplastics (e.g., toxic chemicals present on the surface).

Functional shifts in estuarine zooplankton in response to climate variability.

Functional traits are becoming more common in the analysis of marine zooplankton community dynamics associated with environmental change. We used zooplankton groups with common functional properties to assess long‐term trends in the zooplankton caused by certain environmental conditions in a highly eutrophicated gulf.Time series of zooplankton traits have been collected since the 1960s in the Gulf of Riga, Baltic Sea, and were analyzed using a combination of multivariate methods (principal coordinate analysis) and generalized additive models.One of the most significant changes was the considerable increase in the amount of the zooplankton functional groups (FGR) in coastal springtime communities, and dominance shifts from more complex to simpler organism groups—cladocerans and rotifers.The results also show that functional trait organism complexity (body size) decreased considerably due to cladoceran and rotifer increase following elevated water temperature. Salinity and oxygen had negligible effects on the zooplankton community.

Spatial genetic structure in Themisto libellula (Amphipoda: Hyperiidae) from the coastal Gulf of Alaska, Bering and Chukchi seas

Arctic marine ecosystems are undergoing rapid biogeographic responses to climate changes following the highest warming rates observed around the globe in recent decades. These drastic changes undoubtfully affect gene flow and genetic structure in the polar and subpolar regions. Here, we examine the genetic structure of the cold-water holozooplankton hyperiid Themisto libellula (Amphipoda: Hyperiidae), a key species in the Arctic ecosystem, using molecular population genetic approach. For the first time, we examine and compare populations across the Arcto-Pacific sector of the species biographical range from the northern Gulf of Alaska through the northern Chukchi Sea. We hypothesized that the complex history of the North Pacific and Amerasian Arctic marked by periodic intermissions and restrictions of the dominant northward flow resulted in vicariant differentiation of T. libellula along the latitudinal gradient. Mitochondrial and Rad-sequencing analyses revealed little genetic differentiation between closely connected Arctic populations in the Arctic Chukchi and Bering seas. In contrast, population from sub-Arctic glacial fjords in the Gulf of Alaska were distinct with few shared COI haplotypes. Strong FST estimates (FST = 0.16) based on 5197 neutral SNPs between the Gulf of Alaska and Bering Sea populations indicated very limited exchanges despite an existing connection between the areas via the Alaska Coastal Current. Our results suggest strong opportunities for genetic differentiation among marine zooplankton populations along the Pacific Alaskan coast and from the Arctic marginal seas.

Bioavailability of Microplastics to Marine Zooplankton: Effect of Shape and Infochemicals.

The underlying mechanisms that influence microplastic ingestion in marine zooplankton remain poorly understood. Here, we investigate how microplastics of a variety of shapes (bead, fiber, and fragment), in combination with the algal-derived infochemicals dimethyl sulfide (DMS) and dimethylsulfoniopropionate (DMSP), affect the ingestion rate of microplastics in three species of zooplankton, the copepods Calanus helgolandicus and Acartia tonsa and larvae of the European lobster Homarus gammarus. We show that shape affects microplastic bioavailability to different species of zooplankton, with each species ingesting significantly more of a certain shape: C. helgolandicus-fragments (P < 0.05); A. tonsa-fibers (P < 0.01); H. gammarus larvae-beads (P < 0.05). Thus, different feeding strategies between species may affect shape selectivity. Our results also showed significantly increased ingestion rates by C. helgolandicus on all microplastics that were infused with DMS (P < 0.01) and by H. gammarus larvae and A. tonsa on DMS-infused fibers and fragments (P < 0.05). By using a range of more environmentally relevant microplastics, our findings highlight how the feeding strategies of different zooplankton species may influence their susceptibility to microplastic ingestion. Furthermore, our novel study suggests that species reliant on chemosensory cues to locate their prey may be at an increased risk of ingesting aged microplastics in the marine environment.

Discrimination between freshwater and marine fish using fatty acids: ecological implications and future perspectives

Fatty acids (FA) are a major source of nutrients and energy in aquatic food webs, as well as serving as the main components of all cell membranes. Increasing anthropogenic impacts (e.g., climate change) are predicted to selectively alter the production of these critical compounds, with potential cascading effects reaching higher trophic level organisms, including humans. To provide a more comprehensive assessment of these potential effects, we synthesized and systematically explored differences in the abundance and distribution of FA in fish, due to their pivotal role in aquatic ecosystems and value to humans. An extensive data set consisting of 1382 fish FA profiles was analyzed to identify the main differences in FA composition of freshwater vs. marine fish, taking into account the effects of taxonomic, geographic (i.e., latitude zone), and functional (i.e., feeding mode) factors. Freshwater fish had relatively high contents of 18:2n-6 (linoleic acid, LNA) and 20:4n-6 (arachidonic acid, ARA) indicative of freshwater algae and terrestrial dietary sources. In contrast, 20:1n-9 and 22:1n-11, well known as marine zooplankton biomarkers, typified the FA composition of marine fish. Using this result, we constructed a new metric (i.e., a specific C18–C22 unsaturated FA ratio) that we propose can assist in characterizing the feeding habitat (freshwater vs. marine) and, to some extent, the diet of fish. Our analysis also revealed that carnivores from high latitudes had higher contents of 20:5n-3 (eicosapentaenoic acid, EPA) and 22:6n-3 (docosahexaenoic acid, DHA), thus making them an excellent source of essential FA for human consumption. In parallel, unsaturated FA contents were higher overall at temperate and polar latitudes than in the tropics. The latter two trends may be driven by water temperature variation across latitudes, which is known to affect FA composition of cell membranes in ectotherms. Last, a strong retention of DHA was observed in both freshwater and marine fish. We conclude that our discrimination between freshwater and marine fish provides a quantitative tool that is applicable to a broad range of research and conservation initiatives.

A database of zooplankton biomass in Australian marine waters

Zooplankton biomass data have been collected in Australian waters since the 1930s, yet most datasets have been unavailable to the research community. We have searched archives, scanned the primary and grey literature, and contacted researchers, to collate 49187 records of marine zooplankton biomass from waters around Australia (0–60°S, 110–160°E). Many of these datasets are relatively small, but when combined, they provide >85 years of zooplankton biomass data for Australian waters from 1932 to the present. Data have been standardised and all available metadata included. We have lodged this dataset with the Australian Ocean Data Network, allowing full public access. The Australian Zooplankton Biomass Database will be valuable for global change studies, research assessing trophic linkages, and for initialising and assessing biogeochemical and ecosystem models of lower trophic levels.

Coastal water quality impact on community structure and genotoxicity of marine zooplankton

The present study emphasizes the possible impact of coastal water quality on marine zooplankton community from six different sampling sites of south India (Kalpakkam, Nemmeli, Muttukadu, Kasimedu, Ennore and Kattupalli). Water Samples were collected in the sampling sites and physicochemical parameters were studied. The results showed significant variations in the concentration and distribution pattern of selected physicochemical parameters (temperatures, pH, salinity, DO, NO−3, NO−2, NH3, PO43- and SiO2) and heavy metals (Ni, Cu, Zn, Pb, Fe, Mg, Co, and Cr). The concentration of nutrients and trace elements were reported high at site IV (Kasimedu) and low at site II (Nemmeli). Further, diversity indices showed maximum Shannon_H and Simpson_1-D indexes (H = 3.492; D = 0.966) at site IV (Kasimedu). Similarly, low diversity indices (H = 3.128; D = 0.9508) was registered at site II (Nemmeli) and site III (Muttukadu), indicating plankton population was attracted by high concentration of nutrients loads in the study areas. Finally, genotoxicity (genomic integrity) was assessed by DNA fragmentation and alkaline comet assay, which resulted in maximum genomic integrity loss for the sample collected from Kalpakkam (42.84 ± 08.38), Ennore (41.44 ± 06.59), and Kasimedu (39.5 ± 09.68) sites. The results revealed that the maximum heavy metal concentration has impact on the zooplankton population as evidence from DNA fragmentation compared with that of freshly hatched out Artemia nauplii as control. Hence, the present investigation documents the alarming threat in coastal water quality which will have an impact on the zooplankton community in selected coastal zones.

Short and long-term effects of low-sulphur fuels on marine zooplankton communities

International shipping is responsible for the release of numerous contaminants to the air and the marine environment. In order to reduce airborne emissions, a global 0.5 % sulphur limit for marine fuels was implemented in January 2020. Recently, a new generation of so-called hybrid fuels that meet these new requirements have appeared on the market. Studies have shown that these fuels have physical properties that make conventional clean-up methods difficult, but few have studied their effects on marine life. We conducted short and long-term microcosm experiments with natural mesozooplankton communities exposed to the water accommodated fractions (WAFs) of the hybrid fuel RMD80 (0.1 % sulphur) and a Marine Gas Oil (MGO). We compared the toxicity of both fuel types in 48h short-term exposures, and studied the effects of the hybrid fuel on community structure over two generations in a 28-day experiment.The F0 generation was exposed for eight days and the F1 generation was raised for 22 days without exposure. GC–MS and GC–FID analysis of the WAFs revealed that the hybrid fuel was dominated by a mixture of volatile organic compounds (VOCs) and poly aromatic hydrocarbons (PAHs), whereas the MGO was mainly composed of VOCs. We observed significant short-term effects on copepod egg production from exposure to 25 % hybrid fuel WAF, but no effects from the MGO WAF at equivalent WAF dilution. In the long-term experiment with RMD80, the feeding rate was initially increased after exposure to 0.5–1.1 % hybrid fuel WAF, but this did not increase the copepod egg production. Significant change in community structure was observed after eight days in the F0 community at 0.5–3.3 % WAF. Indications of further alterations in species abundances was observed in the F1 community. Our results demonstrate that the MGO is a less toxic low-sulphur alternative to the hybrid fuel for marine zooplankton, and that a hybrid fuel spill could result in altered diversity of future generations of copepod communities.

Development of metal adaptation in a tropical marine zooplankton

Tropical marine ecosystems are highly vulnerable to pollution and climate change. It is relatively unknown how tropical species may develop an increased tolerance to these stressors and the cost of adaptations. We addressed these issues by exposing a keystone tropical marine copepod, Pseudodiaptomus annandalei, to copper (Cu) for 7 generations (F1–F7) during three treatments: control, Cu and pCu (the recovery treatment). In F7, we tested the “contaminant-induced climate change sensitivity” hypothesis (TICS) by exposing copepods to Cu and extreme temperature. We tracked fitness and productivity of all generations. In F1, Cu did not affect survival and grazing but decreased nauplii production. In F2-F4, male survival, grazing, and nauplii production were lower in Cu, but recovered in pCu, indicating transgenerational plasticity. Strikingly, in F5-F6 nauplii production of Cu-exposed females increased, and did not recover in pCu. The earlier result suggests an increased Cu tolerance while the latter result revealed its cost. In F7, extreme temperature resulted in more pronounced reductions in grazing, and nauplii production of Cu or pCu than in control, supporting TICS. The results suggest that widespread pollution in tropical regions may result in high vulnerability of species in these regions to climate change.

The Harmful Unarmored Dinoflagellate Karlodinium in Japan and Philippines, with Reference to Ultrastructure and Micropredation of Karlodinium azanzae sp. nov. (Kareniaceae, Dinophyceae)1.

In all, 26 cultures of the harmful marine dinoflagellate Karlodinium, isolated from Japanese and Philippine coastal waters, were examined using LM, SEM, and molecular phylogeny inferred from ITS and LSU rDNA. Seven Karlodinium species (six from Japan and four from Philippines), K.australe, K.ballantinum, K.decipiens, K.gentienii, K.veneficum, K.zhouanum, and a novel species Karlodinium azanzae sp. nov., were identified based on their morphology and phylogenetic positions. Karlodinium azanzae from Manila Bay, Philippines was further characterized by TEM, HPLC (chloroplast pigment), and bioassay on brine shrimp and other marine zooplankton. Cells of K.azanzae were the largest (mean 25.3µm long) in Karlodinium, possessed numerous tiny reflective particles, starch grains, and lipid granules, and usually swam at the bottom of the culture vessel. The straight apical structure complex and a ventral pore were common to the genus. The longitudinally elongated nucleus was located at the center, and the yellowish chloroplasts contained an embedded pyrenoid and carotenoid pigments typical of the genus (i.e., fucoxanthin as major carotenoid with its derivatives). TEM revealed a part of the flagellar apparatus, of which the long striated ventral connective is the first report in the Kareniaceae. Phylogenetic trees showed closest affinity of K.azanzae with K.australe and K.armiger. The new species could be differentiated from related species by cell size, position of the nucleus, and characteristic swimming behavior. Lethality of K.azanzae to large zooplankton and micropredation using a developed peduncle was also observed.