Eelgrass detritus as a food source for the sea cucumber Apostichopus japonicus Selenka (Echinidermata: Holothuroidea) in coastal waters of North China: an experimental study in flow-through systems.

Eelgrass ecosystems have a wide variety of ecological functions in which living tissues and detritus may be a food source for many marine animals. In this study, we conducted a laboratory simulating experiment to understand the trophic relationship between the eelgrass Zostera marina L and the sea cucumber Apostichopus japonicus. A mixture of decaying eelgrass debris and seafloor surface muddy sediments was used as food to feed A. japonicus, and then specific growth rates (SGR) and fecal production rates (FPR) were measured. According to the proportion of eelgrass debris, we designed five treatment diets, i.e., ES0, ES10, ES20, ES40, and ES100, with eelgrass debris accounting for 0%, 10%, 20%, 40%, and 100% in dry weight, respectively. Results showed that diet composition had a great influence on the growth of A. japonicus. Sea cucumbers could use decaying eelgrass debris as their food source; and when the organic content of a mixture of eelgrass debris and sediment was 19.6% (ES40), a relatively high SGR (1.54%·d(-1)) and FPR (1.31 g·ind.(-1) d(-1)) of A. japonicus were obtained. It is suggested that eelgrass beds can not only provide habitat for the sea cucumber A. japonicus but can also provide an indirect food source for the deposit feeder. This means that the restoration and reconstruction of eelgrass beds, especially in coastal waters of China, would be a potential and effective measure for sea-cucumber fisheries, in respect to both resource restoration and aquaculture of this valuable species

Herbicide leakage into seawater impacts primary productivity and zooplankton globally

Abstract Predicting the magnitude of herbicide impacts on marine primary productivity remains challenging because the extent of worldwide herbicide pollution in coastal waters and the concentration-response relationships of phytoplankton communities to multiple herbicides are unclear. By analyzing the spatiotemporal distribution of herbicides at 661 bay and gulf stations worldwide from 1990 to 2022, we determined median, third quartile and maximum concentrations of 12 triazine herbicides of 0.18 nmol L−1, 1.27 nmol L−1 and 29.50 nmol L−1 (95%Confidence Interval: CI 1.06, 1.47), respectively. Under current herbicide stress, phytoplankton primary productivity was inhibited by more than 5% at 25% of the sites and by more than 10% at 10% of the sites (95%CI 3.67, 4.34), due to the inhibition of highly abundant sensitive species, community structure/particle size succession (from Bacillariophyta to Dinophyceae and from nano-phytoplankton to micro-phytoplankton), and resulting growth rate reduction. Concurrently, due to food chain cascade effects, the dominant micro-zooplankton population shifted from larger copepod larvae to smaller unicellular ciliates, which might prolong the transmission process in marine food chain and reduce the primary productivity transmission efficiency. As herbicide application rates on farmlands worldwide are correlated with residues in their adjacent seas, a continued future increase in herbicide input may seriously affect the stability of coastal waters

An integrated approach combining chemical analysis and an in vivo bioassay to assess the estrogenic potency of a municipal solid waste landfill leachate in Qingdao.

Various adverse effects related to landfill leachate have made leachates an important issue in past decades, and it has been demonstrated that landfill leachate is an important source of environmental estrogens. In this study, we employed chemical analysis of some already evaluated estrogenic substances, in combination with a bioassay using several specific biomarkers (e.g., plasma vitellogenin and sex steroids, enzyme activity of gonad gamma-glutamyl transpeptidase, and gonadosomatic index) to evaluate the estrogenic activities in outlets from different stages of the leachate treatment process. The results indicated that 5 environmental estrogens (4-t-octylphenol, bisphenol A, di-ethyl phthalate, di-n-butyl phthalate, and diethylhexyl phthalate) were detected by a gas chromatography-mass spectrometry, and the concentrations in leachate samples were 6153 ng/L, 3642 ng/L, 2139 ng/L, 5900 ng/L, and 9422 ng/L, respectively. Leachate (1∶200 diluted) induced the synthesis of plasma vitellogenin and led to decreased enzyme activity of gonad gamma-glutamyl transpeptidase and gonadosomatic index in male goldfish (Carassius auratus) after a 28-day exposure, while increased circulating 17β-estradiol level was also observed in males exposed to treated effluent. Although the target EEs were partially removed with removal rates varying from 87.2% to 99.77% by the "membrane bioreactor+reverse osmosis+aeration zeolite biofilter" treatment process, the treated effluent is still estrogenic to fish. The method combined chemical techniques with the responses of test organisms allowing us to identify the group of estrogen-like chemicals so that we were able to evaluate the overall estrogenic effects of a complex mixture, avoiding false negative assessments

Disruption of the thyroid system by the thyroid-disrupting compound Aroclor 1254 in juvenile Japanese flounder (Paralichthys olivaceus).

Polychlorinated biphenyls (PCBs) are a group of persistent organochlorine compounds that have the potential to disrupt the homeostasis of thyroid hormones (THs) in fish, particularly juveniles. In this study, thyroid histology, plasma TH levels, and iodothyronine deiodinase (IDs, including ID1, ID2, and ID3) gene expression patterns were examined in juvenile Japanese flounder (Paralichthys olivaceus) following 25- and 50-day waterborne exposure to environmentally relevant concentrations of a commercial PCB mixture, Aroclor 1254 (10, 100, and 1000 ng/L) with two-thirds of the test solutions renewed daily. The results showed that exposure to Aroclor 1254 for 50 d increased follicular cell height, colloid depletion, and hyperplasia. In particular, hypothyroidism, which was induced by the administration of 1000 ng/L Aroclor 1254, significantly decreased plasma TT4, TT3, and FT3 levels. Profiles of the changes in mRNA expression levels of IDs were observed in the liver and kidney after 25 and 50 d PCB exposure, which might be associated with a reduction in plasma THs levels. The expression level of ID2 mRNA in the liver exhibited a dose-dependent increase, indicating that this ID isotype might serve as sensitive and stable indicator for thyroid-disrupting chemical (TDC) exposure. Overall, our study confirmed that environmentally relevant concentrations of Aroclor 1254 cause significant thyroid disruption, with juvenile Japanese flounder being suitable candidates for use in TDC studies

Relative mRNA expression levels of thyrotropin-releasing hormone (<i>trh</i>) and corticotrophin-releasing hormone (<i>crh</i>) in the hypothalamus glands and quantification of plasma cortisol content in female goldfish exposed to 0, 0.01, 0.10, and 1.00 mg/L 40% monocrotophos (MCP) pesticide.

<p>(designated C, MCP0.01, MCP0.10, and MCP1.00, respectively). For panels A and B, fold change (Y axis) represents the expression of the target gene mRNA relative to that of the control group (equals 1 by definition). The data are presented as the means ± standard deviations (n = 9). Asterisks indicate statistically significant differences from the control group (*0.01<<i>P</i><0.05, **<i>P</i><0.01).</p

Quantification of plasma free 3,3′,5-triiodo-l-thyronine (T₃) and free 3,3′,5,5′-l-thyroxine (T₄) contents and the relative mRNA expression levels of hepatic transthyretin (<i>ttr</i>) in female goldfish exposed to 0, 0.01, 0.10, and 1.00 mg/L 40% monocrotophos (MCP) pesticide.

<p>(designated C, MCP0.01, MCP0.10, and MCP1.00, respectively). For panel C, fold change (Y axis) represents the expression of the target gene mRNA relative to that of the control group (equals 1 by definition). The data are presented as the means ± standard deviations (n = 9). Asterisks indicate statistically significant differences from the control group (*0.01<<i>P</i><0.05, **<i>P</i><0.01).</p

Mean fecal production rates (FPR; g·ind.

<p>^−<b>1</b><b> d</b>^−<b>1</b><b>) of </b><b><i>Apostichopus japonicus</i></b><b> during the experimental period.</b> Means (n = 4) with different letters denoting significant differences (<i>p</i><0.05), and bars representing standard deviations of the means.</p

Nucleotide sequences of the primers used for real-time polymerase chain reaction and product sizes.

<p>Goldfish contain duplicate genes encoding for D1, D2, and D3, and the primer pairs amplify the two genes.</p><p>Nucleotide sequences of the primers used for real-time polymerase chain reaction and product sizes.</p

Quantification of plasma total 3,3′,5-triiodo-l-thyronine (T₃) and total 3,3′,5,5′-l-thyroxine (T₄) levels in female goldfish exposed to 0, 0.01, 0.10, and 1.00 mg/L 40% monocrotophos (MCP) pesticide.

<p>(designated C, MCP0.01, MCP0.10, and MCP1.00, respectively). The data are presented as the means ± standard deviations (n = 9). Asterisks indicate statistically significant differences from the control group (*0.01<<i>P</i><0.05, **<i>P</i><0.01).</p

Initial and final wet weight (g·ind.⁻¹) of <i>A. japonicus</i> for five diet treatments.

<p>Note: values with different letters in the same row were significantly different from each other (n = 4, <i>p</i><0.05).</p