Search

Storms are among the most common disturbances within coral reef ecosystems. However, their effects on the diversity of reef fishes vary and range from negative to positive. Moreover, storm impacts on spatial heterogeneity of the community are unclear, as an uneven spatial impact can increase heterogeneity, whereas uniform habitat degradation can decrease heterogeneity. Understanding how storms alter the community spatial structure is crucial for evaluating the resilience of reef fish communities across scales. We explored the effect of a strong storm that occurred in March 2020 in the Gulf of Aqaba, where storms are rare. Using data collected from reef knolls surveyed repeatedly since 2015, we analyzed the storm's effects on the structure and spatial heterogeneity of the fish community across multiple scales. We found a post-storm decrease in fish density which dropped to less than half the pre-storm state, along with an increase in community evenness. Yet, the storm impacts differed considerably between sites located less than 5 km apart. We further found that the spatial heterogeneity of the community increased after the storm. However, this was primarily driven by a local reduction in abundance rather than an uneven spatial loss of species. The fish community showed striking recovery and regained baseline richness, abundance, and diversity values within a year. Thus, it appears that although storms may cause short-term increases in spatial heterogeneity, these changes are caused by temporary local losses, and the storm did not produce long-lasting spatial effects on the reef fish community. Additionally, our results suggest the resilience of a reef fish community unaccustomed to storm disturbances. [ABSTRACT FROM AUTHOR]

Habitat utilization is a major component of animal behavior and ecology, yet nighttime habitat utilization by diurnal animals remains understudied for many taxa. Sheltered sleeping sites are considered particularly important for parrotfishes (Labridae: Scarini) inhabiting coral reefs, where predation risk is most prominent at night. Parrotfishes are also known to sleep in mucus cocoons, which allegedly function as a means of predator and/or ectoparasite avoidance. In this study, we present the first systematic characterization of nocturnal habitat utilization and cocoon formation in parrotfishes, in their natural environment. We performed a total of 153 surveys and sampled 225 individual parrotfishes (of 11 species) and characterized their sleeping sites. We found that several species utilized sleeping sites with distinct characteristics, such as exposed sites that provided little to no coverage or sleeping sites well above the reef floor. However, most species exhibited substantial overlap in site characteristics and exposure. We found that the utilization of sheltered sleeping sites did not correlate with body size or life stage, suggesting that sleeping-site selection in parrotfish is unlikely to be driven by competitive exclusion. We also found that while some species either never or rarely formed cocoons, many species exhibited facultative cocoon formation that was not clearly associated with exposure or habitat. While we expected cocoons to be more frequent in exposed sites to avoid predators, or on soft substrates to avoid ectoparasites, we found no effect of either predictor. As many species exhibited a wide range of sleeping sites and behaviors, nocturnal habitat utilization does not appear to be a major axis for niche differentiation in this guild. [ABSTRACT FROM AUTHOR]

The tropical ascidian Herdmania momus (Savigny 1816) has been rapidly expanding its distribution in the Eastern Mediterranean Basin. To examine the role of temperature resilience on its invasion success, we conducted monthly field surveys for two years at Achziv (Israel) Marine Protected Area, and examined the survival of adult individuals from native (Red Sea) and invasive (Mediterranean) populations under different temperature treatments. In addition, temperature effects on fertilization and larval development were examined in controlled laboratory conditions. Results indicate that temperature has a significant effect on H. momus from its early life stages through adulthood. Field surveys revealed a significant decline in H. momus abundance in the Mediterranean with the decrease in seawater temperature. Low temperature inhibited development of early life stages, and individuals from both populations demonstrated low survivability under low temperature treatment. All the above may be derived from the tropical origin of H. momus, and may further limit its dispersal into colder areas. However, adult individuals from the invasive population demonstrated significantly higher survivability to the high temperature treatment in comparison to the native population from the Red Sea. Larvae development, metamorphosis and settlement were enhanced and with higher rates of success under the high temperature conditions. The high-temperature adaptation of the Mediterranean population of H. momus from fertilization to adulthood may thus contribute to its expanding distribution in the Eastern Mediterranean. [ABSTRACT FROM AUTHOR]