Waste heat recovery from shipboard machineries could be a potential source for heat treatment of ballast water. Similar to a shipboard schematic arrangement, a laboratory-scale engine-heat exchanger set-up harvesting waste heat from jacket water and exhaust gases was erected to test the level of species' mortalities. Mortalities were also assessed under experimental conditions for cultured and natural plankton communities at laboratory level. Effect of pump impellers on species' mortalities were also tested. Exposures between 60°C and 70°C for 60 sec resulted in 80-100% mortalities. Mortalities due to pump impeller effects were observed in the range of 70-100% for zooplankton. On the laboratory-scale arrangement, >95% mortalities of phytoplankton, zooplankton and bacteria were recorded. It was demonstrated that the temperature of tropical sea waters used as secondary coolant can be raised to cause species' mortalities, employing engine exhaust gases. The results also indicated that pump impeller effects will enhance species' mortalities. The limitations of the shipboard application of this method would be the large ballast volumes, flow rates and time for treatment.
This study investigates the presence of microplastics in surface seawater and zooplankton at five different locations off the Terengganu coast in Malaysia, southern South China Sea. A total of 983 microplastic particles, with an average abundance of 3.3 particles L-1 were found in surface seawater. An average of one plastic particle was detected in 130 individuals from 6 groups of zooplankton. These groups include fish larvae, cyclopoid, shrimps, polychaete, calanoid and chaetognath where they ingested 0.14, 0.13, 0.01, 0.007, 0.005 and 0.003 particle per individual, respectively. Microplastics in the form of fragments are the most common type of ingested microplastics that ranged between 0.02 mm (cyclopoid) - 1.68 mm (shrimp and zoea). Contrastingly, fibers, which are identified as polyamide are the main type of microplastics that dominate in seawater.
Plankton seasonality in tropical coastal waters is becoming more apparent as a result of monsoon-driven changes in environmental conditions, but research on the monsoonal variation of microplastics (MP) is still limited. We examined the monsoonal variation of MP in the water column and their ingestion by zooplankton in Sepanggar Bay, Sabah, Malaysia. MP concentrations were significantly higher during the Southwest monsoon whereas MP ingestions showed no monsoonal difference across major zooplankton taxa. Canonical Correspondence Analysis (CCA) and Generalized Additive Models (GAM) indicate that MP concentrations were driven by changes in rainfall and salinity while MP bioavailability to zooplankton was consistent regardless of monsoon. MP ingestion increased progressively up the planktonic food chain, and bioavailability of fibers and small-sized MP of high-density polymers to zooplankton was proportionately higher. Distinct changes in the MP concentration relative to the monsoons provide new insights into the seasonal variation of MP in tropical coastal ecosystems.
Seasonal variations of zooplankton community in terms of biomass and size-fractionated densities were studied in a tropical Sangga Kechil river, Matang, Perak from June 2010 to April 2011. Zooplankton and jellyfish (hydromedusae, siphonophores and ctenophores) samples were collected bimonthly from four sampling stations by horizontal towing of a 140-?m plankton net and 500 ?m bongo net, respectively. A total of 12 zooplankton groups consisting of six groups each of mesozooplankon (0.2 mm-2.0 mm) and macrozooplankton (2.0 mm-20.0 cm) were recorded. The total zooplankton density (12375?3339 ind m(-3)) and biomass (35.32?14.56 mg m(-3)) were highest during the northeast (NE) monsoon and southwest (SW) monsoon, respectively, indicating the presence of bigger individuals in the latter season. Mesozooplankton predominated (94%) over the macrozooplankton (6%) during all the seasons, and copepods contributed 84% of the total mesozooplankton abundance. Macrozooplankton was dominated by appendicularians during most of the seasons (43%-97%), except during the NE monsoon (December) when chaetognaths became the most abundant (89% of the total macrozooplankton). BIO-ENV analysis showed that total zooplankton density was correlated with turbidity, total nitrogen and total phosphorus, which in turn was positively correlated to chlorophyll a. Cluster analysis of the zooplankton community showed no significant temporal difference between the SW and NE monsoon season during the study period (> 90% similarity). The present study revealed that the zooplankton community in the tropical mangrove estuary in the Straits of Malacca was dominated by mesoplankton, especially copepods.
Zooplankton samples were collected from the indigenous tropical brackish water lagoon during the wet monsoon (January and February 1990) and the dry monsoon (April and May 1990). The dominant copepod species in the zooplankton community comprising of Oithona sp (especially O. nana and O. robusta) accounted for more than 70% of the zooplankton in January and was gradually replaced by other zooplanktonic species later in the dry season. The lipid contents in zooplankton varied from 0.18 to 1.04% wet weight or 1.14 to 5.92% dry weight respectively. The major fatty acid contents of the zooplankton showed high concentration of 14:0, 16:0, 18:1, 20:5 omega 3 and 22:6 omega 3 especially in the wet season. It also contained high omega-3 highly unsaturated fatty acid series necessary for the growth of commercial fish larvae. It has a better food value than the normally use food organism, brine shrimp; thus reflecting its potential use as food organism for fish larval rearing.
Widespread accumulation and distribution of microplastics at the sea surface raise concerns as the habitat is a feeding ground for zooplankton. As primary consumers, these organisms are closely connected to microplastic input in the marine food chain. Little comparative information currently exists about this problem in estuary and offshore systems. This study investigates microplastic distribution in the surface water and the potential ingestion of microplastics in selected taxonomic groups of zooplankton from the Terengganu Estuary to offshore waters, Malaysia. In the surface water, three types of microplastics were found (fibres, fragments and pellets). Fibres made up the highest percentage, comprising 80.8% and 73.8% of microplastics in offshore waters and estuaries, respectively. The highest total density of microplastics was found in the Terengganu Estuary (545.8 particles m-3). Microplastics sampled from the offshore waters were identified as polyamide, polyethylene, and polypropylene, which possibly originated from secondary microplastic sources. Two types of microplastics were detected in zooplankton: fibres and fragments. Fibres were the most commonly ingested microplastic type in zooplankton collected from offshore waters (94%) and estuaries (77.7%). The average sizes of ingested fibres and fragments were 361.7 ± 226.8 μm and 96.8 ± 28.1 μm, respectively, with a wider range of sizes ingested observed in offshore waters than in estuaries. The concentration of microplastics in seven zooplankton groups varied from 0.01 ± 0.002 particles ind.-1 (Harpacticoida) to 0.2 ± 0.14 particles ind.-1 (Aphragmophora). Notwithstanding the conformity of our results (increased anthropogenic activities led to greater plastic pollution within the estuary), no significant correlation was observed between the levels of microplastic ingestion and microplastic concentration in the surface water within both areas. Our results provide an important baseline reference on microplastic pollution from estuary to offshore waters, as well as proving that zooplankton act as a repository for microplastic in the marine ecosystem.
The distribution and abundance of zooplankton species of Harapan and Aman
Lakes were investigated in relation to physical parameters and chlorophyll-a content. Both
lakes were characterised by the occurrence of algal bloom problem. The composition of
zooplankton was collected at monthly intervals from November 2013 to February 2014.
The total number of taxa in Harapan and Aman Lakes were 23 and 27, respectively.
Rotifera was the highest abundance group represent 64% of the total species recorded
followed by Copepoda (29%) and Cladocera (7%). Three dominant zooplankton that been
recorded in both the lakes are Brachionus forficula, Brachionus nilsoni, and Trichocerca
sp. High abundance of these species indicates that the lakes are eutrophic water bodies.
Overall, zooplankton species distribution and abundance in the study sites are influenced
by various environmental factors such as water transparency and chlorophyll-a content.
A comparison of zooplankton abundance and community in the seagrass and non-seagrass areas of Limau-limauan and Bak- Bak waters within the newly established Tun Mustapha Marine Park was made during 15-17 May 2017. Samples were collected via horizontal tow of a 140 μm plankton net. Environmental variables (temperature, salinity, DO, pH, turbidity) showed no significant differences among the study sites. However, zooplankton showed increasing abundance from non-seagrass, seagrass edge, to seagrass areas at Limau-limauan, while abundance values were comparable among the stations at Bak-bak. Overall zooplankton abundance was significantly higher at the seagrass areas relative to the non-seagrass station at Limau-limauan (p < 0.005), while no statistical difference was found at Bak-Bak (p < 0.21). Mean canopy height was 3-fold higher (p < 0.001) at Limau-limauan than Bak-Bak, suggesting the importance of seagrass bed structural complexity in habitat preference for zooplankton. Cluster analysis revealed the zooplankton community from the seagrass area at Limau-limauan was different from that at seagrass edge and non-seagrass areas, which may be attributed to the influence of seagrass meadows in forming characteristic zooplankton compositions. Marked differences in zooplankton composition and abundance even in close vicinity of sites suggest the importance of local small-scale variations in seagrass habitats in shaping the zooplankton community.
The dinoflagellate genus Alexandrium has been well known for causing paralytic shellfish poisoning (PSP) worldwide. Several non-PSP toxin-producing species, however, have shown to exhibit fish-killing toxicity. Here, we report the allelopathic activity of Alexandrium leei from Malaysia to other algal species, and its toxicity to finfish and zooplankton, via laboratory bioassays. Thirteen microalgal species that co-cultured with Al. leei revealed large variability in the allelopathic effects of Al. leei on the test algae, with the growth inhibition rates ranging from 0 to 100%. The negative allelopathic effects of Al. leei on microalgae included loss of flagella and thus the motility, damages of chain structure, deformation in cell morphology, and eventually cell lysis. The finfish experienced 100% mortality within 24 h exposed to the live culture (2000-6710 cells·mL-1), while the rotifer and brine shrimp exhibited 96-100% and 90-100% mortalities within 48 h when exposed to 500-6000 cells·mL-1 of Al. leei. The mortality of the test animals depended on the Al. leei cell density exposed, leading to a linear relationship between mortality and cell density for the finfish, and a logarithmic relationship for the two zooplankters. When exposed to the treatments using Al. leei whole live culture, cell-free culture medium, extract of algal cells in the f/2-Si medium, extract of methanol, and the re-suspended freeze-and-thaw algal cells, the test organisms (Ak. sanguinea and rotifers) all died at the cell density of 8100 cells·mL-1 within 24 h. Toxin analyses by HILIC-ESI-TOF/MS and LC-ESI-MS/MS demonstrated that Al. leei did not produce PSP-toxins and 13-desmethyl spirolide C. Overall, our findings demonstrated potent allelopathy and toxicity of Al. leei, which do not only pose threats to the aquaculture industry, fisheries, and marine ecosystems but may also play a part role in the population dynamics and bloom formation of this species.
Zooplankton were sampled in Lake Ikeda at a fixed station every month with the aid of a plankton net in order to observe whether cyclomorphism was exhibited by the neonates of Bosmina longirostris. In Lake Ikeda the relative sizes of the antennules and mucrones of B. longrostris neonates decreased in relation to carapace length from 65% in winter to 50% in summer. Mucrone lengths also decreased from 30% in winter to 20% in summer. Both appendages were inversely correlated with surface temperature of the lake. Predation seems to be one of the reasons why neonates of B. longirostris exhibited seasonal cyclomorphism in their antennule and mucrone.
Relationships between six calcifying plankton groups and pH are explored in a highly biologically productive and data-rich area of the central North Sea using time-series datasets. The long-term trends show that abundances of foraminiferans, coccolithophores, and echinoderm larvae have risen over the last few decades while the abundances of bivalves and pteropods have declined. Despite good coverage of pH data for the study area there is uncertainty over the quality of this historical dataset; pH appears to have been declining since the mid 1990s but there was no statistical connection between the abundance of the calcifying plankton and the pH trends. If there are any effects of pH on calcifying plankton in the North Sea they appear to be masked by the combined effects of other climatic (e.g. temperature), chemical (nutrient concentrations) and biotic (predation) drivers. Certain calcified plankton have proliferated in the central North Sea, and are tolerant of changes in pH that have occurred since the 1950s but bivalve larvae and pteropods have declined. An improved monitoring programme is required as ocean acidification may be occurring at a rate that will exceed the environmental niches of numerous planktonic taxa, testing their capacities for acclimation and genetic adaptation.
In the search for better understanding on the nutritional quality of natural tropical plankton, samples were collected from shallow coastal waters facing the South China Sea during the dry monsoon (May-September) and the wet monsoon (November-April) seasons from March 1993 to July 1994. The total fatty acid content of the predominantly phytoplankton communities (25-200 microns sieve nets) varied four to fivefold with the lowest value occurring during the dry monsoon when blue-green became predominant. Saturated fatty acid content (SAFA), polyunsaturated fatty acid (PUFA) and total omega 3 (sigma omega 3) showed the same seasonal pattern as the total fatty acid with high values in October to December 1993. When species of the dinoflagellate Peridinium and Ceratium were present in considerable amount, the docosahexaenoic acid DHA content was high, especially from March to May 1993. The maximum content of eicosapentaenoic acid EPA, total omega-3 fatty acid, PUFA and sigma omega 3 in phytoplankton occurred during the pre-monsoon period (October and November 1993) when the diatoms were present in large amounts. The larger fraction sample (> 200 microns sieve nets) which consisted predominantly of zooplankton had high amounts of PUFA from September to November 1993.
Background. Climate change concurrent with anthropogenic disturbances can initiate serial changes that reverberate up the food chain with repercussions for fisheries. To date, there is no information available concerning the combined effects of global warming and human impacts on tropical marine food webs. While temperate copepods respond differently to warming and environmental stressors, the extent to which tropical copepods can adapt to rising temperature of already warm waters remains unknown. We hypothesize that sea warming and other anthropogenic disturbances over the long term will have the greatest impact on the copepod community in nearshore waters where their effects are accentuated, and therefore vulnerable and resilient species could be identified. Methods. Zooplankton samples were collected during two time periods (1985-86 and 2014-15) interposed by marked anthropogenic disturbances, and at the same five stations located progressively from inshore to offshore in Klang Strait, Malaysia, following the asymmetrical before-after-control-impact (BACI) design. Copepods were identified to species, and results were interpreted by univariate (ANOVA) and multivariate (PERMANOVA, PCO) analyses of the computed species abundance and diversity measures. Results. Copepod total abundance was not significantly different among stations but higher after disturbance than before disturbance. However, changes in the abundance of particular species and the community structure between time periods were dramatic. Coastal large-bodied calanoid species (e.g., Acartia spinicauda, Calanopia thompsoni, Pseudodiaptomus bowmani and Tortanus forcipatus) were the most vulnerable group to disturbance. This however favored the opportunistic species (e.g., Oithona simplex, O. attenuata, Hemicyclops sp., Pseudomacrochiron sp. and Microsetella norvegica). Small-bodied copepods (e.g., Paracalanus sp., Parvocalanus crassirostris and Euterpina acutifrons) were unaffected. Centropages tenuiremis was likely an introduced species. There was no significant loss in species richness of copepods despite the dramatic changes in community structure. Discussion. Sea warming and other human-induced effects such as eutrophication, acidification and coastal habitat degradation are likely the main factors that have altered copepod community structure. The large-bodied estuarine and coastal calanoid copepods are surmised to be vulnerable to eutrophication and hypoxia, while both resilient and opportunistic species are largely unaffected by, or adaptable to, degraded coastal environments and observed sea surface temperature (SST) rise. It is forecasted that SST rise with unmitigated anthropogenic impacts will further reduce large-bodied copepod species the favoured food for fish larvae with dire consequences for coastal fish production.
The possible links between river flow, zooplankton abundance and the responses of zooplanktivorous fishes to physico-chemical and food resource changes are assessed. To this end, the seasonal abundance, distribution and diet of the estuarine round-herring Gilchristella aestuaria and Cape silverside Atherina breviceps were studied in the Kariega Estuary. Spatio-temporal differences were determined for selected physico-chemical variables, zooplankton abundance and zooplanktivorous fish abundance and distribution. Results indicated that, following a river flood event in winter (>30 m3 s-1 ), altered physico-chemical conditions occurred throughout the estuary and depressed zooplankton stocks. Abundance of G. aestuaria was highest in spring, with this species dominant in the upper and middle zones of the estuary, while A. breviceps was dominant in summer and preferred the middle and lower zones. The catch per unit of effort of both zooplanktivores also declined significantly following the flooding, thus suggesting that these fishes are reliant on zooplankton as a primary food source for healthy populations. Copepods dominated the stomach contents of both fish species, indicating a potential for strong interspecific competition for food, particularly in the middle reaches. Temporal differences were evident in dietary overlap between the two zooplanktivorous fish species and were correlated with river flow, zooplankton availability and fish distribution. The findings of this study emphasize the close trophic linkages between zooplankton and zooplanktivorous fishes under changing estuarine environmental conditions, particularly river flow and provide important baseline information for similar studies elsewhere in South Africa and the rest of the world.
At the present time, no artificial larval diet is capable of entirely fulfilling the dietary requirements of several larval fish and crustacean species. Zooplankton live food is the basic foundation of fish larviculture, and successful rearing of fish larvae still heavily depends on an adequate supply of nutritious live food. Despite being important, the production protocols of copepods and cladocerans (Moina) are still underdeveloped in hatcheries. Rotifers and Artemia are the most commonly used live foods. However, these live foods are evidently lacking in crucial nutrient constituents. Hence, through nutrient enrichment, live food with the nutritional profile that meets the requirements of fish larvae can be produced. With the aim to maximize the effectiveness of production to optimize profitability, it is important to evaluate and improve culture techniques for the delivery of micro- and macro-nutrients as feed supplements to larvae in aquaculture systems. Bioencapsulation and enrichment are the evolving techniques in aquaculture that are commonly employed to enhance the nutritional quality of live food by integrating nutrients into them, which subsequently improves the growth, survival, and disease resistance of the consuming hosts. This review aims to highlight some of the approaches and methods used to improve the nutritional quality of live food by modifying their nutrient composition, which could have immense promise in the enhancement of aquatic animal health.
The sex ratio, gonad development and fecundity of Miyakella nepa (Latreille, 1828), in the coastal waters of Pantai Remis, Perak, were investigated from February 2012 to January 2013. Sex identification was done by identifying stomatopod's genitalia organs, and the ovaries were dissected out and preserved for further analysis. Female stomatopods with mature or near spawning stages were used for fecundity estimation. A total of 951 specimens of M. nepa, with 565 females and 386 males were examined. Results showed a sex ratio of 1:1.46 (male:females). Maximum GSI was estimated to be 5.80, while lowest was 2.95. Sexual maturity for female M. nepa was observed at 100 mm total length. The mean fecundity of M. nepa was 425,657 (? 1,8701) eggs which was observed to increase with increased body length.
Zooplankton samples collected before (1985-86) and after (2013-14) the establishment of Kapar power station (KPS) were examined to test the hypothesis that increased sea surface temperature (SST) and other water quality changes have altered the zooplankton community structure. Elevated SST and reduced pH were detected between before and after impact pairs, with the greatest impact at the station closest to KPS. Present PAHs and heavy metal concentrations are unlikely causal factors. Water parameter changes did not affect diversity but community structure of the zooplankton. Tolerant small crustaceans, salps and larvaceans likely benefited from elevated temperature, reduced pH and shift to a more significant microbial loop exacerbated by eutrophication, while large crustaceans were more vulnerable to such changes. It is predicted that any further rise in SST will remove more large-bodied crustacean zooplankton, the preferred food for fish larvae and other meroplankton, with grave consequences to fishery production.
Some diatoms of the genera Pseudo-nitzschia and Nitzschia produce the neurotoxin domoic acid (DA), a compound that caused amnesic shellfish poisoning (ASP) in humans just over 30 years ago (December 1987) in eastern Canada. This review covers new information since two previous reviews in 2012. Nitzschia bizertensis was subsequently discovered to be toxigenic in Tunisian waters. The known distribution of N. navis-varingica has expanded from Vietnam to Malaysia, Indonesia, the Philippines and Australia. Furthermore, 15 new species (and one new variety) of Pseudo-nitzschia have been discovered, bringing the total to 52. Seven new species were found to produce DA, bringing the total of toxigenic species to 26. We list all Pseudo-nitzschia species, their ability to produce DA, and show their global distribution. A consequence of the extended distribution and increased number of toxigenic species worldwide is that DA is now found more pervasively in the food web, contaminating new marine organisms (especially marine mammals), affecting their physiology and disrupting ecosystems. Recent findings highlight how zooplankton grazers can induce DA production in Pseudo-nitzschia and how bacteria interact with Pseudo-nitzschia. Since 2012, new discoveries have been reported on physiological controls of Pseudo-nitzschia growth and DA production, its sexual reproduction, and infection by an oomycete parasitoid. Many advances are the result of applying molecular approaches to discovering new species, and to understanding the population genetic structure of Pseudo-nitzschia and mechanisms used to cope with iron limitation. The availability of genomes from three Pseudo-nitzschia species, coupled with a comparative transcriptomic approach, has allowed advances in our understanding of the sexual reproduction of Pseudo-nitzschia, its signaling pathways, its interactions with bacteria, and genes involved in iron and vitamin B12 and B7 metabolism. Although there have been no new confirmed cases of ASP since 1987 because of monitoring efforts, new blooms have occurred. A massive toxic Pseudo-nitzschia bloom affected the entire west coast of North America during 2015-2016, and was linked to a 'warm blob' of ocean water. Other smaller toxic blooms occurred in the Gulf of Mexico and east coast of North America. Knowledge gaps remain, including how and why DA and its isomers are produced, the world distribution of potentially toxigenic Nitzschia species, the prevalence of DA isomers, and molecular markers to discriminate between toxigenic and non-toxigenic species and to discover sexually reproducing populations in the field.