Extreme climatic events reduce ocean productivity and larval supply in a tropical reef ecosystem

Abstract

Increasing ocean temperatures due to global warming are predicted to have negative effects on coral reef fishes. El Niñ o events are associated with elevated water temperatures at large spatial (1000s of km) and temporal (annual) scales, providing environmental conditions that enable temperature effects on reef fishes to be tested directly. We compared remote sensing data of sea surface temperature (SST) anomalies, surface current flow and chlorophyll-a (Chl-a) concentration with monthly patterns in larval supply of coral reef fishes in nearshore waters around Rangiroa Atoll (French Polynesia) conditions. There was a strong relationship between the timing of the El Niñ o event, current flow, ocean productivity (as measured by Chl-a) and larval supply. In the warm conditions of the event, there was an increase in the SST anomaly index up to 3.5 1C above mean values and a decrease in the strength of the westward surface current toward the reef. These conditions coincided with low concentrations of Chl-a (mean: 0.06 mg m À3 , SE AE 0.004) and a 51% decline in larval supply from mean values. Conversely, during strong La Niñ a conditions when SST anomalies were almost 2 1C below mean values and there was a strong westward surface current, Chl-a concentration was 150% greater than mean values and larval supply was 249% greater. A lag in larval supply suggested that productivity maybe affecting both the production of larvae by adults and larval survival. Our results suggest that warming temperatures in the world's oceans will have negative effects on the reproduction of reef fishes and survival of their larvae within the plankton, ultimately impacting on the replenishment of benthic populations.

Fitoplancton y zooplancton en el área marina protegida de Isla Gorgona, Colombia, y su relación con variables oceanográficas en estaciones lluviosa y seca

“…disminución en la temperatura) o biológicas (aumento en la concentración de alimento) de un área en particular (Lo-Yat et al, 2011;Mackas et al, 2012). Durante el presente estudio, la abundancia del zooplancton se correlacionó positivamente solo con la salinidad superficial.…”

Effects of climate change on fish reproduction and early life history stages

“…As a result, larvae are more susceptible to starvation at higher temperatures and this may explain observations of more variable recruitment and episodes of recruitment failure during periods of anomalously high water temperature. For example, recruitment of most reef fish species failed in French Polynesia during a warm El Niño period (Lo-Yat et al 2011), suggesting that either reproduction or larval survival of a broad range of species was dramatically reduced at high summer temperatures.…”

Impact of El Niño Variability on Oceanic Phytoplankton

“…The larvae of many marine species graze on phytoplankton during this most vulnerable stage of their lives. Hence, changes in phytoplankton population associated with climate variability may propagate rapidly up the marine food chain and profoundly alter the functioning of marine ecosystems (Platt et al, 2003;Edwards and Richardson, 2004;Lo-Yat et al, 2011). In addition, changes in environmental conditions associated with EP and CP El Niño events have been shown to impact mesozooplankton community with variable time lags in the northern California Current, which in turn can affect top down control on phytoplankton, and disrupt the pelagic food chain (Fisher et al, 2015).…”

“…Following EP and CP El Niño events, quite different impact on commercially important fisheries have been reported in anchovy catches in the Humboldt Current Large Marine Ecosystem (Jackson et al, 2011) and tuna catches in the Indian Ocean (Kumar et al, 2014). In coral reef ecosystems, changes in phytoplankton population and mass bleaching following an El Niño event can critically affect fisheries, recreation, and tourism services (Hoegh-Guldberg, 1999;Abram et al, 2003;Lo-Yat et al, 2011). Recent analysis in the Andaman Sea, southeast Bay of Bengal, has further demonstrated that differences both in intensity and timing of SST warming associated with EP and CP El Niño events, can determine the extent of mass coral bleaching (Lix et al, 2016).…”