Ecosystem attributes of trophic models before and after construction of artificial oyster reefs using Ecopath

Abstract

The deployment of artificial reefs (ARs) is currently an essential component of sea ranching practices in China due to extensive financial support from the government and private organizations. Blue Ocean Ltd. created a 30.65 km 2 AR area covered by oysters in the eastern part of Laizhou Bay, Bohai Sea. It is important for the government and investors to understand and assess the current status of the AR ecosystem compared to the system status before AR deployment. We provide that assessment, including trophic interactions, energy flows, keystone species, ecosystem properties and fishing impacts, through a steady-state trophic flow model (Ecopath with Ecosim). The model estimated values of 4721.2 and 4697.276 t km −2 yr −1 for total system throughput and 534.74 and −519.9 t km −2 yr −1 for net system production before and after AR deployment, respectively. After AR deployment, sea cucumber and oyster showed the same trophic level (TL = 2.0) while veined whelk Rapana venosa had TL = 3.0. The mean TL of catches was 2.484 after AR deployment and the primary production required to support fisheries (PPR) was 1104 t km −2 . Detritus production dominated over primary production and represented 73.82% (2530.82 t km −2 ) of total primary production required. The sea cucumber showed the lowest PPR/catch value (5.6) among functional groups, indicating that fishing catch biomasses were close to primary production values. The total primary production to total respiration and total primary production to total biomass ratios showed higher system maturity after AR deployment. The trophic flow diagram showed 1 grazing and 2 detritus food chains. Pelagic and bottom fish and different benthic organisms, including large crustaceans and zoobenthos, were the dominant community before AR deployment. Zoobenthos was the key functional group, followed by large crustaceans and Gobiidae, which were the most important prey for top predators after AR deployment. We draw the following conclusions for the management of this area: (1) AR deployment contributes to the maturity of the improved ecosystem; (2) the artificial oyster system is similar to a natural reef system; (3) the enhancement and release of benthic animals in the AR area benefit the ecosystem; and (4) low TL catches do not cause the system to collapse.

Integrated mRNA and miRNA transcriptomic analysis reveals the response of Rapana venosa to the metamorphic inducer (juvenile oysters)

“…Interestingly, we found that juvenile oysters (shell length less than 3 cm) could effectively stimulate the metamorphosis of R. venosa [13] . Additionally, a previous study indicated that oyster reefs can significantly promote the recovery of R. venosa resources [19] , and the results of our field survey also showed that there were a large number of R. venosa individuals present around oyster reefs. Therefore, oyster reefs promote the recovery of R. venosa resources not only by providing sufficient food for the adults but also by stimulating the metamorphosis of the larvae.…”

“…However, oyster is also one of the most important economic species worldwide [20] , and oyster reefs have significant ecological functions, promoting resource recovery and improving the aquatic environment [19] . Once the number of R. venosa , as a predator, exceeds a certain threshold, oyster resources will be destroyed [21] , so it is of great significance to maintain the number of R. venosa individuals within an appropriate range for stabilizing the ecological balance of oyster reefs.…”

Ecological succession of benthic organisms on niche-type artificial reefs

“…The sessile biota on the NTAR are the first organisms to settle on the available substrate and they perform the function of increasing the complexity of the habitat, offering refuge and food for the fauna that subsequently colonise the structure and whose presence responds to these factors (Antoniadou et al 2011, Antoniadou et al 2010, Dean & Connell 1987b. It is expected that as the niche artificial system spends more time on the sea floor, the changes induced by the development of sessile biota will offer a better habitat and lead to greater abundance of motile fauna, favouring maturity of the ecosystem, as seen in other studies (Xu et al 2019, Higgins et al 2019, Fariñas-Franco & Roberts 2014, Antoniadou et al 2010, Dean & Connell 1987b. It can also be assumed that the presence of the later will be used to identify more clearly a succession pattern that correlates with the coverage of sessile organisms.…”

Examining Epibenthic Assemblages Associated with Artificial Reefs Using a Species Archetype Approach

“…Archetypes and other methods that can accommodate the responses of many species can inform management about the full range of responses to expect when ARs are deployed. Reliance on the responses of focal or target species is useful for understanding how ARs can affect local ecological services (Xu et al 2019) but is insufficient for understanding how other species will respond. When deploying ARs, finding suitable locations is a critical step (Golani and Diamant 1999).…”