Covering

Recent studies have indicated that levels of solar ultraviolet radiation (UVR) are increasing globally as ozone is depleted. Ultraviolet radiation often has negative effects on organism survival; in sea urchins, UVR has been found to reduce sperm motility (reducing fertilization success) and to increase the occurrence of abnormal embryonic development (decreasing embryonic survival). Several species of sea urchins cover themselves with rubble; this study examined how this behavior was affected by UVR in situ. Three types of treatment boxes were placed over Tripneustes ventricosus specimens: a control box, a UVR-blocking box, and an opaque box. Specimens were photographed before and after treatment and percent change in rubble cover was calculated for each individual. The mean change in percent rubble cover presented significant reduction under opaque conditions relative to other treatment conditions (p = 0.005, p = 0.010). There was no significant difference between the latter two treatment groups (p = 0.980). The data suggest that covering behavior in T. ventricosus is not a response specific to UVR, but is a response to light. Further studies of how UVR affects T. ventricosus and as well as how other species cover themselves in response to sunlight and UVR are needed to understand the benefits of covering behavior in elevated UVR climate conditions. Further study on the costs and benefits of covering behavior as well as studies on the covering and sheltering behaviors of other sea urchins is needed to gain a full understanding of how increasing UVR will affect sea urchins.

This student research was retrieved from Physis: Journal of Marine Science XVIII (Fall 2015)19: 27-33 from CIEE Bonaire.

Stressors causing coral reef degradation are making reefs susceptible to domination by other organisms. One documented phase-shift is increased macroalgal cover of deteriorated reefs. Sponges also have the potential to overtake reefs because of their tolerance for rising temperatures and ocean acidification, ability to outcompete corals for space, and tendency to grow on available substrate created by coral mortality. This study aimed to address gaps in the literature on sponge/coral relationships as well as simultaneously study the interactions between coral and both of its potential competitors. Percentage encrusting sponge cover, percentage algae cover, and encrusting sponge density were compared to percentage live, damaged, and dead coral cover to examine the interactions among coral, sponges, and algae. Sponge/coral interactions were also classified to assess sponge aggressiveness. Data was collected at Yellow Submarine dive site using belt transects and photoquadrats. Although no correlations were significant, most comparisons found that sponges and algae decreased with more live coral cover and increased with more dead coral cover. No significant differences among the abundance of sponge/coral interaction types were found on the reef slope, but there were significant differences present on the reef crest. In both locations, most interactions were not aggressive overgrowth interactions. The relationships among sponges, algae, and coral suggest that both sponges and algae tend to grow on substrate made available by coral death. By examining the interactions of both sponges and algae with coral, comparison of these relationships was possible, potentially prompting future work that also assesses multiple ecologically important interactions.

This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 42-51 from CIEE Bonaire.

In a survey of the bathyal echinoderms of the Bahama Islands region using manned submersibles, approximately 200 species of echinoderms were encountered and documented; 33 species were echinoids, most of them widespread in the general Caribbean area. Three species were found to exhibit covering behavior, the piling of debris on the upper surface of the body. Active covering is common in at least 20 species of shallow-water echinoids, but it has been reliably documented previously only once in deep-sea habitats. Images of covered deep-sea species, and other species of related interest, are provided. Some of the reasons adduced in the past for covering in shallow-water species, such as reduction of incident light intensity, physical camouflage, ballast in turbulent water, protection from desiccation, presumably do not apply in bathyal species. The main reasons for covering in deep, dark, environments are as yet unknown. Some covering behavior in the deep sea may be related to protection of the genital pores, ocular plates, or madreporite. Covering in some deep-sea species may also be merely a tactile reflex action, as some authors have suggested for shallow-water species.