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Morphology study of the otoliths of the parrotfish, <i>Chlorurus sordidus</i> (Forsskal, 1775) and <i>Hipposcarus harid</i> (Forsskal, 1775) from the Red Sea coast of Egypt (Family: Scaridae)
No full textIn the present study a comparison of the otolith morphology of two species of parrotfish, family Scaridae, collected from the Red Sea coast of Egypt, is conducted to identify the most appropriate taxonomic characters that separate these species. Ontogenetic changes in the otoliths of the two scarid fishes become evident. In the otoliths of Chlorurus sordidus, the following characters are comparable in small-sized adult fishes: otolith width, otolith depth, mesial surface shape, lateral surface shape, shape of sulcus acusticus, column, rostrum and size of rostrum. The otoliths of young adults (GI) C. sordidus differ from the adult ones in 14 out of the 22 characteristics studied. In the otoliths of Hipposcarus harid, the following characters are comparable in small and large fish: otolith width, otolith depth, mesial and lateral surface shapes, shape of sulcus acusticus, rostrum and size of rostrum
Wind conditions on the Great Barrier Reef influenced the recruitment of snapper (<i>Lutjanus carponotatus</i>)
Get PDFMost coral reef fishes have a pelagic larval stage before recruiting to reefs. The survival of larvae and their subsequent recruitment can drive the dynamics of reef populations. Here we show that the recruitment of the snapper Lutjanus carponotatus to One Tree Island in the Capricorn Bunker Group, in the southern Great Barrier Reef, was highly variable over 23 years. We predicted that the currents in the Capricorn Bunker Group, including their wind driven components and the Capricorn Eddy (a nearby transient oceanic eddy), would affect patterns of recruitment. A biophysical model was used to investigate this prediction. L. carponotatus were collected from One Tree Island and the dates when they were in the plankton as larvae were determined from their otoliths. The winds present during the pelagic phases of the fish were examined; they were found to have survived either longshore (SSE) winds that induced little cross shelf movement in the larval plume or cross shelf (ENE) winds that induced little longshore movement. The unidirectional transportation of the larval plume in these conditions was favorable for recruitment as it kept the plume concentrated in the Capricorn Bunker Group. These winds were more prevalent in the periods of peak L. carponotatus production that preceded high recruitment. Dispersal under average winds (6.2 m s−1 from the prevailing ESE) and strong winds (velocity 1.5 times average), with and without the Capricorn Eddy, was also modeled. Each of these combinations were less favorable for recruitment than the longshore and cross shelf winds larval L. carponotatus survived before reaching OTI. The larval plume was comparatively less concentrated in the Capricorn Bunker Group under average winds. Strong winds transported the larval plume far longshore, to the NW, away from the Capricorn Bunker Group, while the Capricorn Eddy transported larvae seaward into oceanic waters. Larval swimming could counteract these dispersive forces; however, significant dispersion had occurred before larvae developed strong swimming and orientation abilities. This study provides a physical proxy for the recruitment of snapper. Further, we have demonstrated that great insights into recruitment variability can be gained through determining the specific conditions experienced by survivors
Ecotoxicological effects of chemical contaminants adsorbed to microplastics in the clam <i>Scrobicularia plana</i>
Get PDFAlthough microplastics (MPs) are distributed globally in the marine environment, a great deal of unknowns relating to their ecotoxicological effects on the marine biota remains. Due to their lipophilic nature, microplastics have the potential to adsorb persistent organic pollutants present in contaminated regions, which may increase their detrimental impact once assimilated by organisms. This study investigates the ecotoxicological effects of exposure to low-density polyethylene (LDPE) microplastics (11–13 μm), with and without adsorbed contaminants (benzo[a]pyrene—BaP and perfluorooctane sulfonic acid—PFOS), in the peppery furrow shell clam, Scrobicularia plana. Environmentally relevant concentrations of contaminants (BaP−16.87 ± 0.22 μg g−1 and PFOS−70.22 ± 12.41 μg g−1) were adsorbed to microplastics to evaluate the potential role of plastic particles as a source of chemical contamination once ingested. S. plana were exposed to microplastics, at a concentration of 1 mg L−1, in a water-sediment exposure setup for 14 days. Clams were sampled at the beginning of the experiment (day 0) and after 3, 7, and 14 days. BaP accumulation, in whole clam tissues, was analyzed. A multi-biomarker assessment was conducted in the gills, digestive gland, and haemolymph of clams to clarify the effects of exposure. This included the quantification of antioxidant (superoxide dismutase, catalase, glutathione peroxidase) and biotransformation (glutathione-S-transferases) enzyme activities, oxidative damage (lipid peroxidation levels), genotoxicity (single and double strand DNA breaks), and neurotoxicity (acetylcholinesterase activity). Results suggest a potential mechanical injury of gills caused by ingestion of microplastics that may also affect the analyzed biomarkers. The digestive gland seems less affected by mechanical damage caused by virgin microplastic exposure, with the MPs-adsorbed BaP and PFOS exerting a negative influence over the assessed biomarkers in this tissue
Reduced genetic diversity in the clown anemonefish <i>Amphiprion ocellaris</i> in exploited reefs of Spermonde Archipelago, Indonesia
Get PDFPopulations of the clown anemonefish in Spermonde Archipelago, one of the main collection sites for ornamental fish in Indonesia, are potentially overfished, which might lead to a reduction in population size and genetic diversity. Loss of genetic diversity can reduce the adaptability, population persistence and productivity of the targeted species. Therefore, a study investigating the genetic diversity and its potential correlation to population densities of A. ocellaris was conducted. Two islands were chosen as study sites that differed in the degree of exploitation. Barrang Lompo has a high fishing pressure, whereas Samalona has less. Underwater visual censuses showed that population densities in Samalona were threefold higher than in Barrang Lompo (p = 0.005). Analysis of eight microsatellite loci in 364 tissue samples of A. ocellaris revealed that genetic diversity (numbers of alleles, private alleles, and allelic richness) was significantly reduced at the island with high fishing pressure. Allelic richness was also positively correlated with fish density (p < 0.05). These results indicate that ornamental fishery might be a factor contributing to the loss of genetic diversity in A. ocellaris. Therefore, the marine ornamental trade in Spermonde Archipelago needs to be managed (e.g., management of the fishing strategy, implementation of marine protected areas, regular monitoring, and quota determination). Otherwise the populations of A. ocellaris might collapse
Environmental factors influence the detection probability in acoustic telemetry in a marine environment: results from a new setup
Get PDFAcoustic telemetry is a commonly applied method to investigate the ecology of marine animals and provides a scientific basis for management and conservation. Crucial insight in animal behaviour and ecosystem functioning and dynamics is gained through acoustic receiver networks that are established in many different environments around the globe. The main limitation to this technique is the ability of the receivers to detect the signals from tagged animals present in the nearby area. To interpret acoustic data correctly, understanding influencing factors on the detection probability is critical. Therefore, range test studies are an essential part of acoustic telemetry research. Here, we investigated whether specific environmental factors (i.e. wind, currents, waves, background noise, receiver tilt and azimuth) influence the receiver detection probability for a permanent acoustic receiver network in Belgium. Noise and wind speed in relation to distance, the interaction of receiver tilt and azimuth and current speed were the most influential variables affecting the detection probability in this environment. The study indicated that there is high detection probability up to a distance of circa 200 m. A new setup, making use of features that render valuable information for data analysis and interpretation, was tested and revealed general applicability
High-resolution GPS tracking reveals sex differences in migratory behaviour and stopover habitat use in the Lesser Black-backed Gull <i>Larus fuscus</i>
Get PDFSex-, size- or age-dependent variation in migration strategies in birds is generally expected to reflect differences in competitive abilities. Theoretical and empirical studies thereby focus on differences in wintering areas, by which individuals may benefit from avoiding food competition during winter or ensuring an early return and access to prime nesting sites in spring. Here, we use GPS tracking to assess sex- and size-related variation in the spatial behaviour of adult Lesser Black-backed Gulls (Larus fuscus) throughout their annual cycle. We did not find sex- or size-dependent differences in wintering area or the timing of spring migration. Instead, sexual differences occurred prior to, and during, autumn migration, when females strongly focussed on agricultural areas. Females exhibited a more protracted autumn migration strategy, hence spent more time on stopover sites and arrived 15 days later at their wintering areas, than males. This shift in habitat use and protracted autumn migration coincided with the timing of moult, which overlaps with chick rearing and migration. Our results suggest that this overlap between energy-demanding activities may lead females to perform a more prolonged autumn migration, which results in spatiotemporal differences in foraging habitat use between the sexes
CO<sub>2</sub> leakage alters biogeochemical and ecological functions of submarine sands
Get PDFSubseabed CO2 storage is considered a future climate change mitigation technology. We investigated the ecological consequences of CO2 leakage for a marine benthic ecosystem. For the first time with a multidisciplinary integrated study, we tested hypotheses derived from a meta-analysis of previous experimental and in situ high-CO2 impact studies. For this, we compared ecological functions of naturally CO2-vented seafloor off the Mediterranean island Panarea (Tyrrhenian Sea, Italy) to those of nonvented sands, with a focus on biogeochemical processes and microbial and faunal community composition. High CO2 fluxes (up to 4 to 7 mol CO2 m−2 hour−1) dissolved all sedimentary carbonate, and comigration of silicate and iron led to local increases of microphytobenthos productivity (+450%) and standing stocks (+300%). Despite the higher food availability, faunal biomass (−80%) and trophic diversity were substantially lower compared to those at the reference site. Bacterial communities were also structurally and functionally affected, most notably in the composition of heterotrophs and microbial sulfate reduction rates (−90%). The observed ecological effects of CO2 leakage on submarine sands were reproduced with medium-term transplant experiments. This study assesses indicators of environmental impact by CO2 leakage and finds that community compositions and important ecological functions are permanently altered under high CO2
