Effects of Hypoxia on the Distribution of Calanoid Copepod Eggs in the Seabed Sediments of the Eutrophic Masan Bay, Korea

In this study, we investigate the distribution of calanoid copepod eggs in the sediments of Masan Bay (South Sea, Korea), in which hypoxic conditions occur every summer. In August (2011), hypoxia was observed at all stations, while normoxia was observed in April (2012). The pH and hydrogen sulphide concentration at the sediment-water interface in the inner bay during August were 7.7 and >20 mol L−1, respectively, and there was no significant difference between the stations in April. The abundance of eggs in the sediment ranged from 0.69 to 1.49 × 106 eggs m−2 in August, and from 0.59 to 1.08 × 106 eggs m−2 in April. Notably, the proportion of abnormal eggs was high (a maximum of 77.1%) in August, and a uniform distribution of normal eggs (>80%) was observed in April. A generation of abnormal eggs hatched with deformed nauplii in Masan Bay during the summer, and a failure to hatch was likely due to the high H2S concentration and low pH caused by hypoxia. In this paper, we discuss the effects of hypoxia and seabed environments on the hatching success of calanoid copepod eggs.

Marine dinocysts, acritarchs and less well-known NPP: tintinnids, ostracod and foraminiferal linings, copepod and worm remains

Nine non-pollen palynomorph (NPP) groups occur in Quaternary marine and brackish water sediments; these groups represent various planktonic or micro- to macrobenthic organisms. Some extant NPP were previously classified as fossil Acritarcha, Chitinozoa or scolecodonts. We refer to reviews of these fossils and their applications for Paleozoic-Mesozoic biostratigraphy and palaeoecology but focus on extant marine NPP that can be studied by laboratory culture, genetics or micro-geochemical methods. Marine NPP include resting cysts of planktonic dinoflagellates and prasinophytes, tintinnids and other cilates, copepod eggs and skeletal remains, and various microzoobenthos: microforaminiferal organic linings, ostracod mandibles and carapace linings, various worm egg capsules and mouthparts. New micro-Fourier Transform Infrared spectroscopy spectra suggest the probable affinities of the tintinnid cyst type P and Beringiella. Our applications in marine biodiversity and provincialism studies emphasize under-studied polar regions and neglected ice-algae nano-plankton, and compare climate-based NPP distributions to Ocean Biogeographic Information System realms. Trophic relationships are outlined using sediment-trap studies. Seasonal to annual-scale investigations of palaeoproduction provide new perspectives on ocean carbon budgets during times of rapid climate change and atmospheric carbon increase. More taxonomic and source-linkage studies of non-dinocyst marine NPP are needed but we outline potentials for studies of hemispheric or global-scale shifts in marine food webs as driven by ocean warming.

Planktonic Crustacean Culture—Live Planktonic Crustaceans as Live Feed for Finfish and Shrimps in Aquaculture

The cultivation of planktonic crustaceans as live feed is of paramount importance for the aquaculture and aquarium industries. The use of live cladocerans as feed for freshwater fish is limited to the aquarium industry, whereas Artemia and copepods are used to feed edible marine fish larvae with small mouth gape. Live feed production is expensive and time consuming; therefore, it is only used for fish that cannot be fed an inert diet directly, and only until they are ready for weaning to an inert diet. High-quality planktonic crustacean cultures are furthermore used to conduct environmental risk assessments for hazardous chemicals. Cladocerans are widely used for ecotoxicology testing, but Artemia and copepods are emerging as new model species. The present chapter reviews the culturing procedures of these important planktonic crustaceans: Artemia, cladocerans, and copepods. It discusses their use as live feed and as test organisms for environmental risk assessments. The culturing procedures are categorized into three complexity levels: Extensive, semi-extensive, and intensive. In general, the pros for Artemia and cladocerans are that they are easier to culture than copepods. Copepods are often more difficult in term of culture requirements and feeding. Nevertheless, copepods have the advantage of being in either freshwater or saline water, whereas cladocerans are limited to freshwater and Artemia to seawater. Artemia cysts and copepod eggs have a well-defined protocol for storage and distribution to aquaculture end users. Cladocerans, however, have the potential for the ephippia stage, although this is not well developed. For toxicological testing, three species are used: Artemia franciscana, Daphnia magna, and Acartia tonsa, with Artemia and A. tonsa in seawater testing, D. magna in freshwater testing. The chapter concludes with a comparative analysis of these organisms from use and culturing capability and demonstrates that there are strong similarities and challenges across these taxa.

Detection of feeding dietary Rhizostoma pulmo (Macri, 1778) in Samsun coasts of the Black Sea, Turkey

In this study, gastric contents of the medusa Rhizostoma pulmo distributed along the Samsun coast of the Black Sea were investigated between August 2008 and January 2010. Moreover, the relationship between the umbrella diameter and prey selectivity was determined. Captured R. pulmo individuals during the sampling period varied from 14.5 to 42.5 cm in umbrella diameter. The largest umbrella diameter was observed in October in both periods of the present study. Gastric contents of total 231 R. pulmo individuals have been gathered during the sampling period from all stations. 31 taxa, 10 larvae, 2 nauplii and fish and Copepod eggs from 11 phyla have been identified in the gastric contents of R. pulmo individuals. It has been detected that, feeding choices of R. pulmo individuals have differentiated and their food count has increased due to increasing umbrella diameter (according to Spearman rank correlation, r=0.70; p<0.05). According to the gastric content analyses, the feeding dietary of this species predominantly consists of copepods and dinoflagellates. It has been observed that taxa belonging to Crustaceans (59 %; Copepods 45.9 %) and Dinoflagellates (15.4 %) were densely present in the gastric contents gathered from R. pulmo individuals. The Phylum Ciliophora was another abundantly observed group in the gastric content of R. pulmo, with a 7.2 % representation rate. It was determined that jellyfish have a wide range of nutrition from phytoplankton to fish eggs. The sort of prey and amount of nutrition in stomach contents increased in parallel with the umbrella size. It is concluded that R. pulmo has important effects on the pelagic zone of the Black Sea ecosystem.

Phylogeny, evidence for a cryptic plastid, and distribution of Chytriodinium parasites (Dinophyceae) infecting copepods

ABSTRACTSpores of the dinoflagellate Chytriodinium are known to infest copepod eggs causing their lethality. Despite the potential to control the population of such an ecologically important host, knowledge about Chytriodinium parasites is limited: we know little about phylogeny, parasitism, abundance, or geographical distribution. We carried out genome sequence surveys on four manually isolated sporocytes from the same sporangium to analyse the phylogenetic position of Chytriodinium based on SSU and concatenated SSU/LSU rRNA gene sequences, and also characterize two genes related to the plastidial heme pathway, hemL and hemY. The results suggest the presence of a cryptic plastid in Chytriodinium and a photosynthetic ancestral state of the parasitic Chytriodinium/Dissodinium clade. Finally, by mapping Tara Oceans V9 SSU amplicon data to the recovered SSU rRNA gene sequences from the sporocytes, we show that globally, Chytriodinium parasites are most abundant within the pico/nano- and mesoplankton of the surface ocean and almost absent within microplankton, a distribution indicating that they generally exist either as free-living spores or host-associated sporangia.