Massive salp outbreaks in the inner sea of Chiloe Island (Southern Chile): possible causes and ecological consequences

Abstract

ABSTRACT. During 2010 several massive salp outbreaks of the Subantarctic species Ihlea magalhanica were recorded in the inner sea of Chiloé Island (ISCh, Southern Chile), affecting both phytoplankton abundance and salmon farmers by causing high fish mortality. First outbreaks were recorded during February 2010 when Ihlea magalhanica reached up to 654,000 ind m -3 close to the net pens in Maillen Island and consecutive outbreaks could be followed during March and from October to November 2010. One month prior to the first recorded salp outbreak, the adjacent oceanic region and ISCh showed a sharp decline of ca. 1.0ºC in sea surface temperature and an atypical pattern of oceanic sea surface currents, changing from a predominantly meridional (northward) to a zonal (eastward) direction, probably causing a massive Subantarctic Water parcel to enter the ISCh. During the outbreaks, surface chlorophyll concentration decreased from an historical mean of 13.8 to less than 4 mg Chl-a m -3, and did not return to normal conditions throughout the entire year, and similar results were also observed in phytoplankton abundance. The abundance of salp aggregations were highest close to the salmon net pens, which acted as physical barriers, and may have favored the successful reproduction and persistence of the outbreaks during 2010. The possible impact of these outbreaks on phytoplankton quality and quantity, as well as potential scenarios for the development of further outbreaks is discussed.

Integrating multiple data sources for assessing blue whale abundance and distribution in Chilean Northern Patagonia

“…During 2010 and 2012, both models predicted a decrease in BW abundance in CGMC (Figures 3 and 4). For both years, a drop in chl-a concentration during previous spring, a decrease in SST (for 2010), a decrease in the number of TF detected and salp outbreaks were observed ( Figure S1.5, Buchan & Quiñones, 2016;Giesecke et al, 2014;Lara, Saldías, Tapia, Iriarte, & Broitman, 2016). These changes in oceanographic characteristics within CNP were hypothesized to be produced by an atypical pattern of oceanic sea surface currents mediated by negative anomalies in southern annular mode (SAM, Giesecke et al, 2014).…”

“…For both years, a drop in chl-a concentration during previous spring, a decrease in SST (for 2010), a decrease in the number of TF detected and salp outbreaks were observed ( Figure S1.5, Buchan & Quiñones, 2016;Giesecke et al, 2014;Lara, Saldías, Tapia, Iriarte, & Broitman, 2016). These changes in oceanographic characteristics within CNP were hypothesized to be produced by an atypical pattern of oceanic sea surface currents mediated by negative anomalies in southern annular mode (SAM, Giesecke et al, 2014). SAM modulates intraseasonal to interannual changes in atmospheric conditions in the Southern Hemisphere, producing shifts in the westerly winds patterns and a significant decrease in SST in subtropical zones during negative anomalies (Hall & Visbeck, 2002;Marshall 2003;Lovenduski & Gruber, 2005) which did occur during 2010 and 2012 ( Figure S1.6).…”

Blooms of Alexandrium catenella in Coastal Waters of Chilean Patagonia: Is Subantarctic Surface Water Involved?

“…Regarding the relative input of SASW, the ocean offshore of northern Patagonia is sensitive to the latitudinal position of the bifurcation of the west wind drift (WWD) which can be a macro scale indicator of oceanographic and meteorological variability (Gatica et al, 2009). There is also evidence for episodic decreases in sea surface temperature in the Inner Sea of Chiloé associated with a shift of sea surface currents to a zonal direction and the entry of large "parcels" of subantarctic water (Giesecke et al, 2014) which have been responsible for mass occurrence of salps, decreases in chlorophyll-a, and changes in phytoplankton community structure (Giesecke et al, 2014). A weakening in the annual cycle of chlorophyll-a concentration and abnormally cold sea surface temperature in the Inner Sea of Chiloé during 2009-2010 has also been linked to transient large-scale climate forcing (Lara et al, 2016).…”

Environmental drivers of salp Thalia democratica population dynamics from in situ observations

“…They generate episodic but intense downward fluxes of faecal pellets and dead bodies (Lebrato et al 2012, Henschke et al 2013, Smith et al 2014 and serve as prey and/or hosts for many pelagic and benthic organisms (Harbison 1998). Salp blooms can have important economic impacts as well, as high salp densities can (1) negatively impact fish farms (Giesecke et al 2014), (2) clog the cooling systems of power plants and (3) potentially reduce tourism due to their jellyfish-like appearance (Boero et al 2013). These adverse effects explain the growing interest in understanding the mechanisms that drive salp blooms.…”