Recurrent, thermally-induced shifts in species distribution range in the Humboldt current upwelling system

Abstract

a b s t r a c tEl Niño-Southern Oscillation (ENSO) is a global climate variablility, which fundamentally influences environmental patterns of the Humboldt Current System (HCS) off Chile and Peru. The surf clams Donax obesulus and Mesodesma donacium are dominant and highly productive bivalves of exposed sandy beaches of the HCS. Existing knowledge indicates that El Niño (EN, warm phase of ENSO) and La Niña (LN, cold phase of ENSO) affect populations of both species in a different way, although understanding of the mechanisms underlying these effects is still lacking. The aim of this study was to test hypotheses attempting to explain field observations on the effect of strong EN or LN events by using controlled experimental conditions. Growth and mortality rates of both species were registered during a four-week experiment under EN temperature conditions, normal temperature conditions and LN temperature conditions. While D. obesulus exhibited reduced growth and higher mortality under LN conditions, M. donacium showed reduced growth and higher mortality under EN conditions. The results clearly indicate different temperature tolerance windows for each species, possibly reflecting the evolutionary origins of the Donacidae and Mesodesmatidae in regions with contrasting temperature regimes. These results provide experimental support for previous hypotheses suggesting that thermal tolerance is the driving factor behind observed changes in the species distributions of D. obesulus and M. donacium during the extreme phases of ENSO.

Effects of fishing, market price, and climate on two South American clam species

“…In this vein, mass M. donacium mortalities that occurred during strong warm ENSO events have been mainly associated with rising temperatures and increasing susceptibility to parasitism and diseases under anomalous environmental conditions (Arntz et al 1987, Ibarcena et al 2005, Riascos et al 2009. These mass mortalities, which mainly occurred at the northernmost bioclimatic unit, generated drastic changes in the ecosystem and in the macrofaunal community structure, including increasing densities of subordinate competitors, such as the clam Donax obesulus (Arntz et al 1987, Carstensen et al 2010.…”

“…These mass mortalities have been attributed to a number of factors, namely positive sea temperature anomalies, harmful algal blooms, environmental stress, parasitism, and storms (Odebrecht et al 1995, Fiori et al 2004, Riascos et al 2009, Carstensen et al 2010). In the case of M. mactroides, it has been suggested that the effect of these mortalities may swamp management measures (Defeo 2003).…”

Seasonal variability of emerging invertebrate assemblages in a sheltered soft-bottom sublittoral habitat

“…Along the central-south coast of Peru and northern Chile, permanent upwelling changes only incrementally in magnitude during the austral spring and summer (Echevin et al, 2008;Thiel et al, 2007). This pattern contrasts with the strong seasonal upwelling changes in other coastal regions located at the northern (~3°S) and southern (~36°S) extremes of this ecosystem (Chavez et al, 2008;Thiel et al, 2007), and with other coastal systems at similar latitude (Carstensen et al, 2010;Uribe et al, 2012). Seasonal variability in the structure of invertebrate assemblages in this ecosystem appears habitat specific.…”

Variabilidad ambiental y recursos pesqueros en el Pacifico suroriental: estado de la investigacion y desafios para el manejo pesquero

“…En la zona norte de Chile y sur de Perú en particular, la desaparición de grandes poblaciones de macha ha coincidido con la ocurrencia de eventos El Niño intensos (Riascos et al, 2008;Carstensen et al, 2010), con aumentos en la temperatura superficial del mar y disminuciones en salinidad al norte de los 30°S. El rango de distribución de la macha entre los 5°N y la isla de Chiloé (Tarifeño, 1980), se redujo en su extremo norte en cerca de 20° (Arntz et al, 1987) [1982][1983], mientras que durante El Niño 1997-1998 importantes poblaciones de Arica (~18°S) y Coquimbo (~29°55'S) fueron diezmadas, para posteriormente recuperarse (Aburto & Stotz, 2003;Stotz et al, 2005).…”