Chronic and severe hypoxic conditions in Paracas Bay, Pisco, Peru: Consequences on scallop growth, reproduction, and survival

Abstract

The response of Argopecten purpuratus (Peruvian scallop) to environmental conditions was studied in the upwelling-influenced Bay of Paracas (Peru). Scallops growth and reproduction were monitored weekly over a 7-month period under two conditions (culture depths): on the bottom and 2 m above (suspended culture). At the same time, a high-frequency environmental monitoring was realized at the aforementioned depths. The results indicate that environmental conditions in the Bay are highly variable, especially during the summer: temperature fluctuations up to 8∘C were recorded in less than one day while oxic conditions ranged from oversaturation to anoxia. Milky-turquoise waters discoloration events (sulphide presence suspected) were simultaneously observed together with anoxic conditions and sudden temperature drops. Increased stratification and upwelling favorable winds during the summer might be partly responsible for the observed environmental variability. Higher somatic and gonadal growth were observed in scallops growing in suspended culture compare with bottom culture. This pattern might be related to different environmental conditions at culture depth: turbidity was lower in suspended culture and hypoxic conditions occurred only 18% of the whole study period versus 48% on the bottom. The Gonadosomatic index varied according to an approx. 30-day cycle between winter and late spring and it was synchronous between the different scallop size groups. During summer, when milky waters and anoxic events occurred frequently, cessation of reproduction, somatic weight losses and increased scallop mortality were observed. Exposure to severe hypoxia and related environmental conditions clearly affected scallop bioenergetics and subsequently growth and reproduction. In addition, the occurrence of milky waters harmed the survival of the Peruvian scallop in culture. These results are discussed in terms of management strategies for sustainable scallop aquaculture in the Bay. Highlights ► High frequency environmental recording in Paracas bay (Peru) showed frequent and chronic hypoxic conditions. ► Exposure to severe hypoxia and related environmental conditions clearly affected scallop bioenergetics and subsequently growth and reproduction. ► Milky-turquoise waters events affect negatively survival of Peruvian scallop

Attenuation of wind intensities exacerbates anoxic conditions leading to sulfur plume development off the coast of Peru

“…Porewater analysis of sulfide and sulfate concentrations from cores recovered at stations S2 and S3 (in Paracas Bay) showed patterns consistent with previous ETSP sediment studies [ 47 , 62 ]. From April to June, the vertical profiles (down to 20 cm) of pore water H 2 S (0–5 mM) and SO 4 2- (20–29 mM) exhibited a wide range of concentrations ( Fig 4A–4D ; S4A and S4B Fig , S2 Table ).…”

“…6m depth), next to the San Martin Harbor, by the environmental monitoring program of the PLUSPETROL Company [ 46 ] ( Fig 7C ). The difference between surface and bottom water temperature (ΔT °C) has been previously used as a proxy of water stratification [ 47 ] ( Fig 7D ).…”

The Clam Before the Storm: A Meta Analysis Showing the Effect of Combined Climate Change Stressors on Bivalves

“…Negative growth responses though generally repeat across the taxa in our dataset irrespective of habitat. An intertidal habitat or preference for marine or brackish water does not appear to alter observed growth responses in the experimental setting to accumulated climate stressors, as we find consistent decreases in growth rates, and commonly subtidal, epifaunal bivalves (such as many Pectinidae) also exhibiting significant negative responses (Aguirre-Velarde et al, 2019;Maynou et al, 2020). Interpreting the effects of ecology on our results is complicated by the previously mentioned dominance of studies focused on juvenile and early growth stages; many bivalves feature a veliger or early larval stage that live in and can tolerate quite different environmental https://doi.org/10.5194/egusphere-2023-287 Preprint.…”

Hypoxia in the Blue Mussel Mytilus chilensis Induces Transcriptome Shift Associated with Endoplasmic Reticulum Stress, Metabolism, and Immune Response.

“…Exposure to hypoxia may also have repercussions beyond cellular biochemistry [84]. In bivalve mollusks, hypoxia can inhibit gonadal development [131]. These effects can be attributed to changes in energy balance due to hypoxia, which, in turn, negatively affects reproduction and population dynamics [132].…”