A low-volume submersible drift-pump unit is described for the collection of demersally drifting biota, particularly for shallow aquatic situations. This unit collects less motile biota quantitatively ...(so far zooplankton, larvae of macrofauna, and meiofauna are successfully collected). It can easily be modified for the sampling of a variety of other aquatic organisms, in particular nano- and picoplankton (algal, bacterial, fungal and viral plankton) at high temporal and spatial resolution. A new drift-net unit allows qualitative comparisons of demersally drifting invertebrates. Both light-weighted stationary systems can be modified for sampling at varying distances from the bottom and are suggested for fine-scale appliances at moderate depths from shore, pier, boat, or deployed by divers.
Microcystins are cyanobacterial hepatotoxins, and are produced by nonribosomal enzyme complexes,
mcy
gene cluster. In this study, we report on whole
mcy
gene clusters from two Korean strains of
M. ...aeruginosa
that were blooming in Lake Paldang (FCY-26) and Geum river (FCY-28). Their specific gene locus, amino acid information, and sub-cluster orientation were also characterized in both strains. Both gene clusters are of 55 kb, and also each length, number and the arrangement are identical. Their sequence analysis revealed a cluster of 10 genes (
mcyA
,
B
,
C
,
D
,
E
,
F
,
G
,
H
,
I
, and
J
) involved in the biosynthesis of microcystin, and
mcyABC
and
mcyDEFGHIJ
formed two polycistronic operon structures that are transcribed bidirectionally from a central promoter region between
mcyA
and
mcyD
. The analysis of SNPs provided different nucleotide composition and amino acid variations in two Korean strains of
M. aeruginosa
. This approach is useful to develop genetic indicators identifying toxic cyanobacteria and their cyanotoxins, and helpful for a better understanding of the diversities of
mcy
gene clusters, the biosynthesis of microcystin, and the mediation of environmental parameters causing algal blooming and HABs.
This study reports significant differences in larval settlement of the polychaeteHydroides elegans(Haswell, 1883) on biofilms treated either by different densities of live harpacticoid copepods or ...conditioned by particulate organic material (POM) retrieved from harpacticoid copepod cultures. The copepods used in this study were the facultatively predatoryTisbe japonicaand the detritivorousNitocra spinipes. The resulting biofilms covering experimental surfaces exhibited differences in bacterial abundances, bacterial community profiles and bioactivity, as evidenced by differential attractivity provided as percentages of larval settlement. The density of settled larvae decreased on biofilms modified by increasing numbers of copepods. The highest bacterial densities (16 085 ± 915 cells mm–2) were found on natural biofilms conditioned with POM from cultures ofT. japonica. The lowest bacterial densities (4020 ± 765 cells mm–2) were found on biofilms grown in the presence of the highest numbers of liveT. japonica. Spearman-rank correlation results revealed a positive trend between increasing bacterial densities and larval settlement. Increasing copepod abundances were correlated with reduced bacterial densities and caused changes in the bacterial community profiles, which were identified by terminal restriction fragment analyses. Changes in microbial biofilms due to the conditioning effects of copepods or their remains/exudates are assumed to be responsible for differential larval settlement. Hence, the present laboratory study demonstrates that effects of predators can be mediated by biofilms and affect larval settlement indirectly.
The meiobenthos along a depth transect of oligotrophic sediments in the Arctic Laptev Sea was studied. The meiobenthos followed the general trends reported from other studies: densities decreased ...with depth in relation to the more limited supply of degradable organic matter at greater depths. Although the sediments along the transect were poor in organic matter in comparison with the NE Atlantic, the densities fitted well with the meiobenthic densities reported from the latter area. It is suggested that the meiobenthos in the cold polar waters is adapted to this extreme environment by a rapid response to short food pulses to the sediments. Nematodes were identified up to genus level and assigned to trophic groups. A total of 32 families comprising 95 genera were found along the transect. The communities were dominated by deposit feeders whose importance increased with depth. Both TWINSPAN and CCA analyses revealed a community shift along the depth transect: a shelf community dominated by Microlaimus and Chromadora could be distinguished from a slope community dominated by Monhystera and Leptolaimus. Generic diversity decreased with depth.
Development of microbial biofilms and the recruitment of propagules on the surfaces of man-made structures in the marine environment cause serious problems for the navies and for marine industries ...around the world. Current antifouling technology is based on the application of toxic substances that can be harmful to the natural environment. For this reason and the global ban of tributyl tin (TBT), there is a need for the development of "environmentally-friendly" antifoulants. Marine microbes are promising potential sources of non-toxic or less-toxic antifouling compounds as they can produce substances that inhibit not only the attachment and/or growth of microorganisms but also the settlement of invertebrate larvae and macroalgal spores. However, so far only few antilarval settlement compounds have been isolated and identified from bacteria. In this review knowledge about antifouling compounds produced by marine bacteria and diatoms are summarised and evaluated and future research directions are highlighted.
Extreme temperatures from marine heatwaves (MHWs) and pollution are dominant stressors in tropical marine ecosystems. However, we know little about the role of transgenerational effects of metals and ...MHWs in shaping the offspring's vulnerability to these stressors. We addressed this fundamental knowledge gap by exposing the planktonic copepod Pseudodiaptomus incisus to copper (Cu: control, 15 and 60 μg L−1) under 2 temperatures (30 and a simulated marine heatwave at 34 °C) in the first generation (F1) and 16 treatments in F2: offspring from each of 4 F1 conditions (control or 15 μg Cu L−1 × 30 or 34 °C) was reared in 4 F2 conditions (control or 15 μg Cu L−1 × 30 or 34 °C). We assessed changes in copepod performance, particularly survival, adult size, grazing, and reproduction. In F1, Cu or marine heatwave (MHW) exposures reduced all fitness traits of F1; the effects were particularly strong when both stressors were present. Transgenerational effects of Cu or MHW also strongly reduced F2 performance. Direct Cu and MHW effects on the offspring were further strengthened by transgenerational effects, resulting in more substantial reductions in F2 performance when both generations were exposed to these stressors. As copepods are major food resources for corals, shrimps, or fish larvae and juveniles, strong transgenerational and direct effects of Cu and MHW can have a cascading effect on entire coastal food webs. These results highlight the importance of considering the interaction of transgenerational and direct effects of multiple stressors, particularly relevant for short-lived organisms in tropical marine ecosystems.
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•Marine heatwaves (MHW) and pollution are dominant stressors in the tropics.•MHW increases the toxicity of copper on tropical copepod Pseudodiaptomus incisus.•Parental exposure to MHW increases offspring vulnerability to MHW and Cu.•Parental exposure to Cu increases offspring vulnerability to MHW and Cu.
Single and combined effect of metals and marine heatwaves on the parental generation of marine copepods reduce the capacity of offspring to cope with these stressors.
Cyanobacteria produce a variety of bioactive metabolites that may have allelochemical functions in the natural environment, such as in the prevention of fouling by colonising organisms. Chemical ...compounds from cyanobacteria are also of biotechnological interest, especially for clinical applications, because of their antibiotic, algicidal, cytotoxic, immunosupressive and enzyme inhibiting activities. Cyanobacterial metabolites have the potential for use in antifouling technology, since they show antibacterial, antialgal, antifungal and antimacrofouling properties which could be expoited in the prevention of biofouling on man-made substrata in the aquatic environment. Molecules with antifouling activity represent a number of types including fatty acids, lipopeptides, amides, alkaloids, terpenoids, lactones, pyrroles and steroids. The isolation of biogenic compounds and the determination of their structure may provide leads for future development of, for example, environmentally friendly antifouling paints. An advantage of exploring the efficacy of cyanobacterial products is that the organisms can be grown in mass culture, which can be manipulated to achieve optimal production of bioactive substances. Phycotoxins and related products from cyanobacteria may serve as materials for antimicro- and antimacrofouling applications. A survey of antibiotic compounds with antifouling potential revealed more than 21 different antifouling substances from 27 strains of cyanobacteria.
We analyse the influence of the Kuroshio Current on copepod assemblages in the northern South China Sea. The assumption was tested whether predominant current regimes bring marine zooplankton and ...Copepoda from subtropical and tropical waters to the south of Taiwan. A total of 101 copepod species were identified from 26 families and 48 genera that include Calanoida, Cyclopoida, Harpacticoida and Poecilostomatoida. High copepod abundances in the study area are shown to be caused by both, a year-round Kuroshio Current intrusion and the SW monsoon, prevailing in the South China Sea during summer.
Calanus sinicus did not appear in the samples, indicating that there was no cold water mass intrusion in the area during sampling. Both, the intrusion of the Kuroshio Branch Current to the Luzon Strait and the South China Sea circulation may play a more important role in shaping copepod assemblages in the region than hitherto expected. The abundance of copepods was higher above the 50 m isoline than at deeper strata. Species number and the Shannon–Wiener diversity index were higher with increasing depth. Copepod assemblage structure changed with different sampling depth and different sampling areas. Copepod abundance and species richness were higher in the northern South China Sea than in the Kuroshio Current area, and higher at lower latitudes than at higher latitudes. Some indicator species are characteristic for the Kuroshio Current and indicate with others that the study area accomodated water masses from the northern South China Sea as well as from the Kuroshio Current.
