Direct and indirect effects of simulated calcareous dredge material on eggs and larvae of pink snapper Pagrus auratus

Abstract

The direct and indirect effects of a simulated, calcarenite-based dredge material on eggs and larvae of pink snapper Pagrus auratus were assessed. Direct effects were assessed by measuring hatch rate or survival of eggs and pre-feeding larvae, respectively, over a range of concentrations and exposure durations. Exposure of eggs to suspended solid concentrations up to 10 000 mg l(-1) for 24 h did not affect egg buoyancy or hatch rate, despite sediment adherence occurring at the two highest concentrations tested. Newly hatched larvae, whose mouths were still closed, were relatively tolerant of suspended solids, with a 12 h lethal concentration resulting in 50% mortality, LC(50), of 2020 mg l(-1) and a first observable effect concentration of 150 mg l(-1). Once the larvae's mouths opened, tolerance was significantly reduced, with a 12 h LC(50) of 157 mg l(-1) and a first observable effect concentration of 4 mg l(-1). Tolerance of larvae to suspended solids was negatively correlated with suspended solids concentration and exposure time, with exposure durations of <or=6 h being significantly less detrimental than those of 9 h or more. Indirect effects to larvae were assessed by measuring ingestion of copepod nauplii by 10 and 15 days post-hatch (dph) larvae at sediment concentrations from 0 to 200 mg l(-1) in 50 mg l(-1) increments over 4 h. Ingestion was not significantly affected by sediment for 10 dph larvae, but by 15 dph, sediment had a far greater impact on ingestion, with larvae in all sediment treatments eating significantly fewer copepods than those in the control.

Turbidity reduces hatching success in Threatened Spotted Gar (Lepisosteus oculatus)

“…Suspended sediments can effectively smother eggs, depriving them of oxygen and leading to egg mortality (reviewed in Henley et al 2010). Some studies, however, have shown little negative effects of suspended sediment on the egg stage, whereas, larval stages are severely adversely affected by turbidity (e.g., Isono et al 1998;Partridge and Michael 2010). Therefore, the effect of turbidity on fish eggs may be species specific (reviewed in Henley et al 2010), and it may be that imperilled species are those that are most sensitive to this stressor, while more common species are able to compensate.…”

Effects of offshore wind farms on marine wildlife—a generalized impact assessment

“…On the other hand, gravity foundations involve higher impact from sediment dispersal, due to dredging. Although organisms inhabiting wave-exposed sites typical for OWF establishment can generally be expected to be tolerant of turbidity, some studies indicate that elevated turbidity may harm sensitive organisms, such as juvenile fish (Auld and Schubel 1978, Lake and Hinch 1999, Partridge and Michael 2010. The impact of sediment dispersal was rated low to moderate, with good to moderate certainty (table 2).…”

Digitise This! A Quick and Easy Remote Sensing Method to Monitor the Daily Extent of Dredge Plumes

“…Construction of pipelines, marinas and ports within these coastal environments often requires land reclamation and dredging of the sea floor with subsequent spoil disposal. The suspension of sediments due to these activities potentially has impacts on surrounding ecosystems, such as physical smothering of benthic communities, and decreased light availability which limits growth and metabolic processes of sea grass [1], algae [2], coral [3], [4] [5], [6] and larval fish [7]. Scientists and management agencies are under growing pressure to be able to understand the spatial extent and potential influences, particularly cumulative, of these activities within short time frames (daily) to enable appropriate response measures.…”