Evaluating deep-sea communities' susceptibility to mining plumes using shallow-water data.

Increased suspended sediment concentrations (SSC) are a major stressor across aquatic habitats. Here, the literature was synthesized to show that animal responses to increases in relative SSC (test concentration/natural background concentration) were similar in type and negative across different shallow-water (marine, estuarine, freshwater) habitats. Further, animal sensitivities are similar across habitats based on relative SSC and occur starting at low relative SSC increases in all habitats despite differences in natural background SSC. Based upon these similarities in relative SSC sensitivities, deep-sea sensitivity values for acute exposure to increased SSC, where empirical data are almost non-existent, were estimated. Because of the low natural SSC in deep sea environments, very small increases in absolute SSC could result in acute effects. How the methods and results can be used to inform regulatory thresholds are discussed. Because of the large variability in shallow water datasets and differences between deep-sea and shallow-water habitats, deep-sea specific data are needed to verify the estimates and improve their precision. Following the precautionary principle and the results presented here, it is recommended that the threshold for acute plume impacts is set very close to natural background levels.

Paraliparis hawaiiensis, a new species of snailfish (Scorpaeniformes: Liparidae) and the first described from the Hawaiian Archipelago.

Paraliparis hawaiiensis n.sp. is described from the north-western Hawaiian Islands from two specimens collected at 2196 and 3055 m. It differs from other North Pacific Ocean species in its chin pore arrangement, tooth pattern and body proportions. Although liparid specimens have previously been collected from Hawaii, they were undescribed and are now lost. Therefore, this is the first liparid species described from the archipelago. In situ photographs of Hawaiian snailfishes are also shown and discussed here.

Red muscle proportions and enzyme activities in deep-sea demersal fishes.

Owing to the paucity of data on the red muscle of deep-sea fishes, the goal of this study was to determine the proportions of red muscle in demersal fishes and its enzymatic activities to characterize how routine swimming abilities change with depths of occurrence. Cross sectional analysis of the trunk musculature was used to evaluate the proportion of red muscle in 38 species of Californian demersal fishes living at depths between 100 and 3000 m. The activity of metabolic enzymes was also assayed in a sub-set of 18 species. Benthic fishes had lower proportions of red muscle and lower metabolic enzyme activities than benthopelagic species. Mean proportion of red muscle declined significantly with depth with the greatest range of values in shallow waters and species with low proportions found at all depths. This suggested that while sedentary species occur at all depths, the most active species occur in shallow waters. Citrate synthase activity declined significantly with depth across all species, indicating that the mass-specific metabolic capacity of red muscle is lower in deep-sea species. These patterns may be explained by coupling of red and white muscle physiologies, a decrease in physical energy of the environment with depth or by the prevalence of anguilliform body forms and swimming modes in deep-living species.