A critical review of the potential impacts of marine seismic surveys on fish & invertebrates.

Marine seismic surveys produce high intensity, low-frequency impulsive sounds at regular intervals, with most sound produced between 10 and 300Hz. Offshore seismic surveys have long been considered to be disruptive to fisheries, but there are few ecological studies that target commercially important species, particularly invertebrates. This review aims to summarise scientific studies investigating the impacts of low-frequency sound on marine fish and invertebrates, as well as to critically evaluate how such studies may apply to field populations exposed to seismic operations. We focus on marine seismic surveys due to their associated unique sound properties (i.e. acute, low-frequency, mobile source locations), as well as fish and invertebrates due to the commercial value of many species in these groups. The main challenges of seismic impact research are the translation of laboratory results to field populations over a range of sound exposure scenarios and the lack of sound exposure standardisation which hinders the identification of response thresholds. An integrated multidisciplinary approach to manipulative and in situ studies is the most effective way to establish impact thresholds in the context of realistic exposure levels, but if that is not practical the limitations of each approach must be carefully considered.

UV-induced mortality in encapsulated intertidal embryos: are mycosporine-like amino acids an effective sunscreen?

Mycosporine-like amino acids (MAAs) are believed to protect a variety of marine organisms against the negative effects of ultraviolet radiation (UVR). However, their role in protecting developing intertidal encapsulated embryos remains untested. In the present study, we focused on the UV protective role of natural concentrations of MAAs for two intertidal gastropod species, Bembicium nanum and Siphonaria denticulata, which lay egg masses in habitats exposed to direct sunlight. We predicted that in both species, a higher concentration of MAAs within the egg mass would increase the likelihood of embryonic survivorship in the presence of UVR. Egg masses from both species were collected along the rocky shores of southeastern New South Wales, and a portion from each was subjected to one of three separate spectral treatments: full spectrum, UV-B block, and UV block. Proportions of surviving embryos were recorded following 72 hr exposure to spectral treatment. In addition, MAAs in each egg mass were quantified. Levels of variation in MAA concentration were striking, with S. denticulata egg masses showing more intraspecific variation than those of B. nanum. Surprisingly, survivorship under all spectral treatments was extremely high for both species, irrespective of MAA concentration. Under full spectrum treatments, B. nanum survivorship and total MAA concentration were significantly and positively correlated; however, MAA accounted for just 23.6% (R = 0.486) of the variation in survivorship. In contrast, survivorship in S. denticulata was not correlated with MAA concentration under full spectrum light. We conclude that the dependence on MAAs as photoprotection may be species-specific; however, it is likely that both species possess alternative mechanisms that minimize the negative effects of UVR.

A quantitative survey of mycosporine-like amino acids (MAAS) in intertidal egg masses from temperate rocky shores.

Mycosporine-like amino acids (MAAs) have been reported as functional chemical sunscreens in a variety of marine organisms, but their role in development of marine embryos and larvae remains largely unexplored. In this study, we quantified MAAs from intertidal egg masses of 46 species of mollusks, two species of polychaetes, and one species of fish from southeastern Australia. We aimed to elucidate potential patterns of occurrence and variation based on egg mass maturity, adult diet, spawning habitat, phylogeny, and viability. Our analyses revealed that maturity and spawning habitat did not affect MAA composition within egg masses. In contrast, adult diet, phylogeny, and viability affected MAA composition. Herbivores had higher levels of certain MAAs than carnivores; similarly, viable egg masses had higher levels of some MAAs than inviable ones. MAA composition varied according to the taxonomic group, with nudibranchs and anaspids showing different MAA composition compared to that of neogastropods, sacoglossans, and polychaetes. Basommatophoran egg masses had more porphyra-334 than the other taxa, and anaspids had more mycosporine-2-glycine than the other groups. MAAs occurred in relatively high concentrations in intertidal molluskan egg masses when compared to adult mollusks and other common intertidal organisms. Despite the complexity of factors affecting MAA composition, the prevalence of MAAs in some species is consistent with protection afforded to offspring against negative effects of UV radiation.