Recovery of eutrophized marine ecosystems using the European flat oyster, Ostrea edulis

Abstract

1. The development of tourism and intensification of agriculture has released large amounts of nitrogen and phosphorus into the Mar Menor coastal lagoon in South-east Spain, resulting in a phytoplankton bloom in 2016. This bloom turned the clear and transparent waters turbid and greenish, and killed approximately 85% of benthic macrophytes.2. Nutrient bioextraction by flat oysters, Ostrea edulis, has been proposed for remediation of these eutrophication events and water quality recovery.3. This research aims to quantify the clearance rate and investigate the genetic origin of Mar Menor oysters under eutrophized conditions for potential applications to bioremediation projects. Oligotrophic and eutrophic conditions were replicated in the laboratory, and oyster feeding behaviour (i.e. clearance rates, ingestion rates, absorption efficiency and absorption rates) were studied using a flow-through system. 4. The genetic characterization of oysters showed no significant difference between individuals from the Mar Menor and individuals collected from a nearby Mediterranean bed (Tabarca Island). 5. Based on the physiological results observed, oysters were grouped into highfeeder (HF) and low-feeder (LF) categories according to their clearance rate, that was 3-fold higher in the HF group. Different responses in feeding behaviour were observed under eutrophic conditions in both oyster groups. Constraints in the absorption capacity of LF oysters seemed to be related to their reduced filtering activity. Lower body condition of LF oysters was evidenced by their negative scope for growth value.6. From this work, several conclusions can be drawn for future restoration/ bioextraction actions: (i) the recovery of half of the oyster population that existed in the past would act as an effective top-down control on the phytoplankton community; (ii) using clearance rate measurements is recommended to select

Hatchery seed production of flat oysters from the Mar Menor lagoon

“…This study concluded that the species was O. edulis, which exhibited a genetic diversity similar to those described for other European oyster beds and were genetically related to the Mediterranean oysters near the MM (Albentosa et al, 2023). After this initial study (Albentosa et al, 2023), the MMOI focused on building an experimental oyster hatchery for seed production using water from the lagoon itself. The use of seawater from the MM to supply the hatchery may have represented an additional challenge to the inherent difficulties of flat osyter seed production (Colsoul et al, 2021).…”

“…The adults collected had a mean length of 93.1 ± 12.1 mm, height of 106.1 ± 14.3 mm, and width of 41.4 ± 8.1 mm. The mean wet weight (WW) was 230.2 ± 74.4 g, with a mean dry weight (DW) of 1.6 ± 0.4 g [the DW was estimated through length-DW relationships estimated from individuals dissected in the study of Albentosa et al, (2023)].…”

“…In terms of biosecurity, the best recommendation for seed production is to use local broodstock and water (Fitzsimons et al, 2020;zu Ermgassen et al, 2020c). With the purpose of using local breeders, Albentosa et al, (2023) collected some adult oyster specimens from the lagoon in order to determine their potential nutrient extraction capacity, species identity, and genetic diversity and their proximity to other flat oyster populations in Europe. This study concluded that the species was O. edulis, which exhibited a genetic diversity similar to those described for other European oyster beds and were genetically related to the Mediterranean oysters near the MM (Albentosa et al, 2023).…”

“…With the purpose of using local breeders, Albentosa et al, (2023) collected some adult oyster specimens from the lagoon in order to determine their potential nutrient extraction capacity, species identity, and genetic diversity and their proximity to other flat oyster populations in Europe. This study concluded that the species was O. edulis, which exhibited a genetic diversity similar to those described for other European oyster beds and were genetically related to the Mediterranean oysters near the MM (Albentosa et al, 2023). After this initial study (Albentosa et al, 2023), the MMOI focused on building an experimental oyster hatchery for seed production using water from the lagoon itself.…”

Northern Europe’s suitability for offshore European flat oyster (Ostrea edulis) habitat restoration based on population dynamics

“…An important model assumption (Table 1) is that population size does not influence the environment of the site. Oyster populations generally influence the environment by regulating food levels (Akinyemi et al, 2021;Albentosa et al, 2023), providing suitable substrate for settlement (Rodriguez-Perez et al, 2019), increasing complexity of the seabed which improves larval retention (Andutta et al, 2012) or attracting biodiversity including oyster predators. These relationships with the environment define carrying capacity or maximum population size.…”