Applying behavioral studies to the ecotoxicology of corals: A case study on Acropora millepora

Abstract

Behavioral responses are considered sensitive and effective indicators of organism stress. As the demand for standardized coral toxicity tests grows, innovative tools that allow for automatic and quantitative measurements of these behaviors may complement ecotoxicological studies. The rapid growth of competitive marine algae in aquaculture systems is a major issue for generating coral spat for reef restoration, and the application of non-toxic antifouling (AF) coatings might effectively mitigate this issue. While these coatings do not appear to be toxic to sensitive coral larvae, their potential to affect larval mobility has not been tested. In this context, we tested the effect of three recently-developed and potentially non-toxic AF coatings: (i) antiadhesive, (ii) cerium dioxide (CeO2-x) nanoparticle, and (iii) encapsulated biocide dichlorooctylisothiazolinone (DCOIT) on the swimming velocity and activity of Acropora millepora coral larvae for potential use in reef-restoration activities. The behavior of 32 coral larvae per AF treatment were recorded, each for 25 min, in a self-constructed dark box with two camera recording sets in parallel. The tracking analysis was performed with the software Noldus EthoVision XT. The mean larval swimming velocity on control tiles of 93.1 ± 5.6 mm min-1 (and activity of 62.8 ± 5.2%) was nearly 2-fold faster (higher) than on the antiadhesive, (CeO2-x) nanoparticle and DCOIT coatings, respectively. Larvae exposed to the DCOIT-coated tiles remained almost stationary. Although the underlying cause and consequence of these results require further investigation, tracking of coral larval swimming behavior was identified as a reliable and feasible method for assessing potential non-lethal responses to AF coatings. As changes in behavior could have significant consequences for larval survival and settlement, they are important endpoints to consider, and the quantification of behavioral responses may be a meaningful and sensitive tool. Therefore, we recommend the use of behavioral studies for coral larval assessments in ecotoxicology as a valuable endpoint. For methodological standardization and implementation, our study also features a detailed guide for video-processing and track analysis of A. millepora coral larvae in EthoVision.

Adults of Sun Coral Tubastraea coccinea (Lesson 1829) Are Resistant to New Antifouling Biocides

“…As antifouling biocides, the tested substances were expected to inhibit and strongly intoxicate fouling organisms, as reported for marine temperate species [ 17 , 18 ] and juveniles of P. perna [ 1 ], but they seemed to not be as effective against adults of T. coccinea . Recently, Roepke et al [ 42 ] studied the toxicity of DCOIT (free and encapsulated forms in cerium oxide nanoparticles) and observed that the antifouling inhibited algal fouling but did not affect coral larval settlement. Still, the lack of effects even at the highest concentrations (i.e., at magnitudes of milligrams per liter) shows that T. coccinea is highly tolerant to the AF biocides tested, another advantage aiding its spread along the Brazilian coast, including at seaports [ 43 ] and recreational marinas [ 44 ], where the concentration of antifouling biocides might be high.…”

Adults of Sun-Coral <em>Tubastraea coccinea </em>Are Resistant to New Antifouling Biocides

“…As antifouling biocides, the tested substances were expected to inhibit and strongly intoxicate fouling organisms, as reported to marine temperate species [17,18] and juveniles of P. perna [1], but they seemed to not be so effective against adults of T. coccinea. Recently, Roepke et al [40] studied the toxicity of DCOIT (free and encapsulated forms in cerium oxide nanoparticles) and observed that the antifouling inhibited algal fouling but did not affect coral larval settlement. Still, the lack of effects even at the highest concentrations (i.e., at magnitudes of milligrams per liter) shows that T. coccinea is highly tolerant to AF biocides tested, another advantage to its spread along the Brazilian coast, including at seaports [41] and recreational marinas [42], where the concentration of antifouling biocides might be high.…”

The Study of Caspian Roach (Rutilus caspicus) Fry Health Fed with Phytobiotic-Supplemented and Salinity Stress Resistance with Emphasis on Gill Tissue Pathology

“…Behavioral reactions are an indicator of aquatic sensitivity to stress and gills are sensitive to environmental stress due to direct contact with the aquatic environment. So, in ecotoxicological research, behavior is a valuable end point as a result of physiological changes affected by environmental pollutants [11,12]. Therefore, histopathological changes in gills can be used as a marker to evaluate the effects of salinity on fish.…”