Physiological Characteristics of Stylophora pistillata Larvae Across a Depth Gradient

Abstract

Depth related parameters, specifically light, affect different aspects of corals physiology, including fluorescence. Green fluorescence protein (GFP)-like pigments found in many coral species have been suggested to serve a variety of functions, including photo-protection and photo-enhancement. Using fluorescence imaging and molecular analysis, we further investigated the role of these proteins on the physiology of the coral Stylophora pistillata and its algal partners. Fluorescence was found to differ significantly between depths for larvae and adult colonies. Larvae from the shallow reef presented a higher GFP expression and a greater fluorescence intensity compared to the larvae from the mesophotic reef, reflecting the elevated need for photo-protection against high light levels characteristic of the shallow reef, thus supporting the "sunscreen" hypothesis. Additionally, given the lower but still occurring protein expression under non-damaging low light conditions, our results suggest that GFP-like proteins might act to regulate the amount of photosynthetically usable light for the benefit of the symbiotic algae. Moreover, we propose that the differences in GFP expression and green fluorescence between shallow and deep larvae indicate that the GFPs within coral larvae might serve to attract and retain different symbiont clades, increasing the chances of survival when encountering new environments.

Long-term and large-scale spatiotemporal patterns of soundscape in a tropical habitat of the Indo-Pacific humpback dolphin (Sousa chinensis)

“…Snapping shrimp "snaps" were observed constantly in each recording file at all sites, with frequencies above 2 kHz (Fig 9B). Dolphin "clicks" were sporadically recorded in frequencies above 20 kHz (Fig 9A), confirming that dolphin sounds are a minor component in the variation of the soundscape in Hainan waters [47,48]. Species-specific identification of the sounds produced by dolphins was not applied in this work.…”

“…The observed "clicks" were considered to be mainly from IPHD in this study, while further investigation to classify the sounds from other possible species that emit similar sounds is deserved. However, previous studies [48] claimed that the presence of dolphin clicks has a very little influence on the variation of the soundscape…”

“…The species has already been classified as "Vulnerable" by the International Union for Conservation of Nature (the IUCN Red List of Threatened Species 2018). Recently, PAM studies reported that distribution, acoustic behavior, and habitat use of IPHD in this area are strongly influenced by the abundance of soniferous fishes and the species seemed to be more acoustically active in locations with lower levels of noise [47,48]. Research on the log-term and large-scale variation of soundscape in Hainan waters would help to better understand the marine acoustic environment and eventually benefit the conservation of IPHD.…”

“…In two sites of waters off Taiwan, China, two frequency bands (150-300 Hz and 1.2-2.4 kHz) were studied during a 3-month monitoring, and it was reported that the lower frequency band was mainly associated with container vessels at one site, while the higher frequency band was from fish chorus at nighttime in both sites [49]. The variation of soundscape in the Pearl River Estuary waters was studied during a 16-day monitoring and reported a significant variation in diel and tidal soundscapes, but with the majority of IPHD sounds detected during periods without fish sounds [48]. However, in that specific study the acoustic monitoring was conducted during a very short monitoring period.…”

“…Although these studies provided important regional information about the acoustic space occupied by IPHD, a long-term and large-scale spatiotemporal analysis is needed to generate a comprehensive understanding of its habitat [47,48]. Different waters have different soundscape signatures related to distinctive physical and biological features [49,51].…”