Muddied waters: suspended sediment impacts on gill structure and aerobic scope in an endangered native and an invasive freshwater crayfish

Abstract

Suspended sediment (SS) loadings in freshwater habitats have increased over the past century and SS is now a significant environmental stressor. Greater tolerance to environmental stressors has been proposed as a factor in the success of aquatic invasive species. Further, parasites may interact with environmental stressors to increase host susceptibility to loss of fitness and mortality. We compared the effects of SS exposure on the gill structure and aerobic scope of the endangered white-clawed crayfish (Austropotamobius pallipes), and the invasive signal crayfish (Pacifastacus leniusculus), and assessed impacts in relation to parasite burden. SS caused gill fouling and reduction in aerobic scope in both species, though A. pallipes was more susceptible than invasive P. leniusculus. The parasite Branchiobdella astaci, a crayfish worm that infests the gills, interacted with the sediment to affect gill structure whereas infection with the microsporidian parasite Thelohania contejeani had no effect on crayfish response to SS. Juvenile P. lenisuculus had a higher standard metabolic rate than A. pallipes, which may be linked to competitive advantages such as higher growth rate and behavioural dominance. Conservation of A. pallipes often involves relocation of threatened populations to isolated stillwaters; our findings suggest that SS levels should be assessed before relocation.

The importance of biotic entrainment for base flow fluvial sediment transport

“…However, alterations to suspended sediment concentrations as demonstrated here may facilitate further advantages over native species because Rosewarne et al . [] have shown that A. pallipes are significantly less tolerant of suspended sediment than signals, suffering greater gill fouling, gill damage, and reduced aerobic scope across a range of sediment concentrations. Therefore, the ecosystem engineering activities of P. leniusculus may have contributed to their invasive success.…”

Measuring maximum and standard metabolic rates using intermittent‐flow respirometry: a student laboratory investigation of aerobic metabolic scope and environmental hypoxia in aquatic breathers

“…If crayfish rather than fish are tested, a two‐stage exhaustion protocol is adopted (Rosewarne et al , ). Individual crayfish are placed in a shallow tray (40 cm × 25 cm × 4 cm) of water at the experimental temperature and induced to tail flip by repeatedly touching the tail fan (telson) with the blunt end of a pencil.…”

“…The unit for oxygen consumption rate in equation (3) is mg O 2 kg −1 h −1 (Steffensen et al , ). A value of A = 0·8 is commonly used for fishes (Holeton, ; Skov et al , ) and A = 0·71 for crayfish (McFeeters et al , ; Rosewarne et al , ), although species‐specific values should be used when available [see Table SII (Supporting Information) for sample calculations].…”

Water chemistry and endangered white-clawed Crayfish: a literature review and field study of water chemistry association inAustropotamobius pallipes

“…No information exists regarding the long term status of this population, and this level of TSS may be a result of habitat degradation. A laboratory study by Rosewarne et al (2014) found that levels above 500 mg·L −1 resulted in gill fouling in all exposed crayfish (A. pallipes), whilst 250 mg·L −1 was associated with fouling in 92% of exposed individuals. However, the same study did not find any reduction in survival over 45 days in concentrations up to 1000 mg·L −1 , indicative of at least short-term tolerance for extremely high levels.…”