El Niño drives a widespread ulcerative skin disease outbreak in Galapagos marine fishes

Abstract

Climate change increases local climatic variation and unpredictability, which can alter ecological interactions and trigger wildlife disease outbreaks. Here we describe an unprecedented multi-species outbreak of wild fish disease driven by a climate perturbation. The 2015–16 El Niño generated a +2.5 °C sea surface temperature anomaly in the Galapagos Islands lasting six months. This coincided with a novel ulcerative skin disease affecting 18 teleost species from 13 different families. Disease signs included scale loss and hemorrhagic ulcerated patches of skin, fin deterioration, lethargy, and erratic behavior. A bacterial culture isolated from skin lesions of two of the affected fish species was identified by sequencing of the 16S rRNA gene as a Rahnella spp. Disease prevalence rates were linearly correlated with density in three fish species. In January 2016, disease prevalence reached 51.1% in the ring-tailed damselfish Stegastes beebei (n = 570) and 18.7% in the king angelfish Holacanthus passer (n = 318), corresponding to 78% and 86% decreases in their populations relative to a 4.5-year baseline, respectively. We hypothesize that this outbreak was precipitated by the persistent warm temperatures and lack of planktonic productivity that characterize extreme El Niño events, which are predicted to increase in frequency with global warming.

Factors linked to interannual variation in the metazoan parasite communities of black skipjack, Euthynnus lineatus (Pisces: Scombridae)

“…The present PCA results (Figure ) strongly suggest that interannual variations in local environmental factors (i.e., temperature, salinity, climate season, and ENSO index) had a substantial effect on parasite infracommunity structure. For example, infracommunity parameter values were significantly lower in the 2015 sampling (Table ), during one of the strongest recent ENSO events in the Pacific region, which generated an abnormally high temperature increase of up to +2.5°C in some regions of the tropical Pacific (Lamb et al, ). During this climate event, surface temperature (30.2°C) and salinity (35.5 ppt) in Acapulco Bay were significantly higher than in other sampling years (Table ).…”

“…During this climate event, surface temperature (30.2°C) and salinity (35.5 ppt) in Acapulco Bay were significantly higher than in other sampling years (Table ). Abnormal increases in sea surface temperature can decrease the productivity of food webs, affecting the parasite transmission processes of many trophically transmitted parasites due to population decreases in potential intermediate or final hosts (Lamb et al, ; Jacobson et al, ; Oliva et al, ). In Acapulco Bay slight changes in the temperature and salinity parameters can be enough to generate notable changes in copepod community species composition throughout the year (Rojas‐Herrera, Violante‐Gonzalez, Garcia‐Ibañez, Villerias‐Salinas, & Moreno‐Diaz, ).…”

“…One of the most ubiquitous patterns in parasite ecology is high variability in parasite infection levels between populations of the same host species (Bagee, Poulin, & Valtonen, ; Marcogliese, ). Changes in local environmental factors, whether physical, oceanographic, or chemical, can facilitate the establishment and proliferation of certain parasites over time (Bagee et al, ; Jacobson et al, ; Lamb et al, ; Oliva et al, ). Therefore, local fluctuations in surface temperature and salinity, as well as changes in the diet of fish over time, may explain interannual variations in the infection levels of N. euthynni , C. caballeroi , H. ventricosa , Sicuotrema sp., Rhadinorhynchus sp., Anisakis sp., and Spinitectus sp.…”

“…During the most recent El Niño event (2015–2016), sea surface temperature rose by +2.5°C for 6 months in tropical regions such as the Galapagos Islands in the South Pacific. This abnormally high surface temperature was associated with the appearance of an ulcerative skin disease affecting several fish species in this region (Lamb et al, ).…”

The 2015-2016 El Niño increased infection parameters of copepods on Eastern Tropical Pacific dolphinfish populations

“…Several studies have shown that climate change strongly affects performance, population dynamics and distribution of marine organisms [6,17,18,19]. In particular, ENSO affects host-pathogen relationships of some marine organisms by reducing host immunity and increasing pathogen virulence [8,16,19,20,21,22]. However, most of these studies have been carried out on fungal, viral, protozoan [8,22,23,24,25] or internal metazoan parasites [9,26,27], while ectoparasites, which are more exposed and influenced by environmental variables, remain poorly studied.…”