The 2016 red tide crisis in southern Chile: Possible influence of the mass oceanic dumping of dead salmons

Abstract

In 2016, a massive harmful algal bloom (HAB) of Alexandrium catenella around Chiloé island caused one of the major socio-ecological crisis in Chilean history. This red tide occurred in two distinct pulses, the second, most anomalous, bursting with extreme toxicity on the Pacific coast, weeks after the highly controversial dumping off Chiloé of 4,700 t of rotting salmons, killed by a previous HAB of Pseudochattonella verruculosa. We study the transport of this pollution, analyzing the physical oceanographic conditions during and after the dumping. We find that a cyclonic gyre was present between the dumping site and the coast, visible in satellite altimetry and sea surface temperature data. Using Lagrangian simulations, we confirm that near-surface currents could have brought part of the pollution to the coast, and fueled the bloom. This scenario explains also the anomalous later finding of ammonium near Chiloé. Finally we discuss the mismanagement of risk throughout the events. Highlights► Some rotting salmon biomass could have fueled the extraordinary 2016 red tide. ► A cylconic gyre was present between the pollution location and Chiloé's coast. ► Part of the salmon pollution off Chiloé could have reached coastal surface waters. ► Transported salmon biomass can explain the coastal ammonium patch found later.

Protocols for Monitoring Harmful Algal Blooms for Sustainable Aquaculture and Coastal Fisheries in Chile

“…Our measured chl- a in the water was 15.05 μg/L, and the water transparency on the day was 3.5 m. These values were in line with Aiken [ 36 ], who reported a chl- a of 3 μg/L in Puerto Montt water in April 2010, during the non-bloom period ( Figure 7 in [ 36 ]). It should be noted that chl- a values vary broadly based on the water condition, and it can be between a μg to mg per liter scale in southern Chile [ 38 , 39 ].…”

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

“…Media reports immediately implicated a variety of potential causative factors for the A. catenella bloom such as (1) the dumping 130 km offshore of rotting salmon killed by the P. verruculosa bloom (2) the sharp recent increase in aquaculture activities in the region (3) the coinciding of the bloom with the 2016 El Niño. Although the role of disposed salmon was later dismissed (Buschmann et al, 2016), it has been suggested that this dumping may have been related to a secondary peak in A. catenella (Armijo et al, 2020). The complexity of factors involved mean that we remain unable to rationalize the specific factors behind either this specific catastrophic event, or the general trends of bloom formation and toxicity of A. catenella throughout southern Chile.…”

A Twitter-Lived Red Tide Crisis on Chiloé Island, Chile: What Can Be Obtained for Social-Ecological Research through Social Media Analysis?

“…Within this context, Chiloé is a widely employed case study on the sustainability of fishing ecosystems, especially in association with the sustainability of salmon and shellfish aquaculture and their environmental and social impacts on the island and its population [114][115][116][117][118]. The 2016 events have contributed to boosting this literature, with new contributions multiplying in recent years, covering long-term socio-cultural and social-ecological trends and transformations contributing to explain the crisis [44,119,120], the specific influence played by the salmon dumping on the crisis [46]; local perceptions on the crisis and its relationship with climate and environmental change [121] and the different frames employed in media coverage of the crisis [47,122]. Noticeably, only one of these studies [48] makes use of social media analyses, and as we observe in detail in the next section, it is focused on the limited use of these platforms for concrete political actions than on the evolution of social media communications as a way to understand the underlying dynamics of the crisis.…”

“…In a previously published article [42], the authors have analyzed this event in detail mostly under an actor-centered qualitative approach with a few elements of social media research. In the meantime, other researchers have applied similar methods to explore this case [43][44][45], while others conducted a more structure-centered research, whether referring to quantitative ecological data [41,46] or to communicative consequences [47,48]. Considering this, we argue that the case of the 2016 red tide crisis on Chiloé Island, is a well-suited case for identifying the novel knowledge that can be gained for social-ecological research when conducting social media analysis with a multi-method approach.…”