High Mortality of Red Sea Zooplankton under Ambient Solar Radiation

Abstract

High solar radiation along with extreme transparency leads to high penetration of solar radiation in the Red Sea, potentially harmful to biota inhabiting the upper water column, including zooplankton. Here we show, based on experimental assessments of solar radiation dose-mortality curves on eight common taxa, the mortality of zooplankton in the oligotrophic waters of the Red Sea to increase steeply with ambient levels of solar radiation in the Red Sea. Responses curves linking solar radiation doses with zooplankton mortality were evaluated by exposing organisms, enclosed in quartz bottles, allowing all the wavelengths of solar radiation to penetrate, to five different levels of ambient solar radiation (100%, 21.6%, 7.2%, 3.2% and 0% of solar radiation). The maximum mortality rates under ambient solar radiation levels averaged (±standard error of the mean, SEM) 18.4±5.8% h−1, five-fold greater than the average mortality in the dark for the eight taxa tested. The UV-B radiation required for mortality rates to reach ½of maximum values averaged (±SEM) 12±5.6 h−1% of incident UVB radiation, equivalent to the UV-B dose at 19.2±2.7 m depth in open coastal Red Sea waters. These results confirm that Red Sea zooplankton are highly vulnerable to ambient solar radiation, as a consequence of the combination of high incident radiation and high water transparency allowing deep penetration of damaging UV-B radiation. These results provide evidence of the significance of ambient solar radiation levels as a stressor of marine zooplankton communities in tropical, oligotrophic waters. Because the oligotrophic ocean extends across 70% of the ocean surface, solar radiation can be a globally-significant stressor for the ocean ecosystem, by constraining zooplankton use of the upper levels of the water column and, therefore, the efficiency of food transfer up the food web in the oligotrophic ocean.

Comparative metatranscriptomics reveals decline of a neustonic planktonic population

“…1). Laboratory experiments have already shown that UV-B levels in the region in June increase the mortality of zooplankton in the Red sea (Al-Aidaroos et al 2014. An increase in the expression of genes involved in oxidative stress for copepods indicates that it is one of the expected effects of UV-B (Lesser 2006).…”

Ecological Study of the Rabigh Lagoon, Eastern Site of the Red Sea, Saudi Arabia with Special Reference to Eutrophication Index

“…He also noticed that 19 species of copepods were highly abundant in the Red Sea. Al-Aidaroos [22] reported that, the increasing the mortality of zooplankton were associated with the high illumination of the sun light especially in oligotrophic basin.…”

“…Pearman [22][23][24] focused in his research about zooplankton communities were associated with coral reefs. On the other hand, Cornils [25], stated that Calanoid copepods were found to dominate subtropical mesozooplankton communities of the northern part of the Red Sea.…”

Adverse Effects of Ultraviolet Radiation on Growth, Behavior, Skin Condition, Physiology, and Immune Function in Gilthead Seabream (Sparus aurata)

“…The impacts of UVB in marine biota are expectedly more severe in oligotrophic and highly transparent waters, mostly due to deeper UVB penetration (Morel et al, 2007;Al-Aidaroos et al, 2014;Garcia-Corral et al, 2015;Overmans and Agustí, 2019). From an economic point of view, the damage caused by UVB on sensitive species can result in a decline of harvesting in fisheries, and also significant losses in the aquaculture sector (Zagarese and Williamson, 2001;Barnes et al, 2019;Williamson et al, 2019).…”