Invading oysters and native mussels: from hostile takeover to compatible bedfellows

Abstract

Citation: Reise, K., C. Buschbaum, H. B€ uttger, and K. M. Wegner. 2017. Invading oysters and native mussels: from hostile takeover to compatible bedfellows. Ecosphere 8(9):e01949. 10. 1002/ecs2.1949 Abstract. Unintended species introductions may offer valuable insights into the functioning of species assemblages. A spectacular invasion of introduced Pacific oysters Magallana (formerly Crassostrea) gigas in the northern Wadden Sea (eastern North Sea, NE Atlantic) has relegated resident mussels Mytilus edulis on their beds to subtenant status. At the beginning of feral oyster establishment, mussel beds offered suitable sites with ample substrate to settle upon. After larval attachment to mussels, the fast-growing M. gigas overtopped and smothered their basibionts. With increasing Pacific oyster abundance and size, oyster larvae preferentially settled upon oysters, and the ecological impact of the invaders on the residents changed from competitive displacement to accommodation of mussels underneath a canopy of oysters. Oysters took the best feeding positions while mussels received shelter from predation and detrimental epibionts. The resident's mono-dominance has turned into co-dominance with an alien, persisting in novel, multi-layered mixed reefs of oysters with mussels, which we term "oyssel reefs." The first 26 yr of the Pacific oyster's conquest of mussel beds in the northern Wadden Sea may question the overcome notions of natural balance, superiority of pristine over novel species combinations, and of introduced alien species threatening biodiversity and ecosystem stability in general.

Return of the native facilitated by the invasive? Population composition, substrate preferences and epibenthic species richness of a recently discovered shellfish reef with native European flat oysters (Ostrea edulis) in the North Sea

“…Also, in Lake Grevelingen co-existence of both species is well documented on the basis of landing data of both species that are cultivated on bottom plots in the area. In both the Dutch as well as the German part of the Wadden Sea, mussel beds were invaded by alien Pacific oysters, changing the reef from a mono-species (M. edulis) bed into a two-species multi-layered mixed reef of oysters and mussels (around 1990;Reise et al 2017b;Nieuwhof 2018). This co-existence of native and invasive bivalves provided refuge against predation for a higher abundance of the native mussel, and possibly also for the native oyster.…”

How Do They Do It? – Understanding the Success of Marine Invasive Species

“…Furthermore, anthropogenic derived disturbances and the introduction of new species are skewing food webs towards a loss of higher trophic groups and a gain in lower order consumers (Byrnes et al 2007). On the other hand, the invasion of marine NIS may increase local biodiversity, as marine invaders often appear to accommodate besides native species rather than replacing them (Briggs 2007; an example in Reise et al 2017). As a higher biodiversity stabilizes communities, invaders may also have overall positive effects, especially in otherwise disturbed habitats.…”

How invasive oysters can affect parasite infection patterns in native mussels on a large spatial scale

“…A suitable model system to investigate the relative importance of invasive species in determining infection levels in native hosts in the field, is the invasion of the Pacific oyster (Magallana gigas) along north western European coasts. This bivalve was introduced to Europe in the 1960s to replenish native oyster stocks for aquaculture purposes (Troost 2010), and today Pacific oyster populations co-occur with native blue mussels (Mytilus edulis) in dense bivalve beds on intertidal mudflats (Reise 1998;Troost 2010;Ruesink et al 2005;Buschbaum et al 2016;Reise et al 2017). Pacific oysters co-introduced the invasive parasitic copepod Mytilicola orientalis that was likely co-introduced in large numbers or via multiple introductions and followed a similar invasion route as oysters (Feis, 2018) and subsequently spilled over to native blue mussels (Pogoda et al 2012;Goedknegt et al 2017).…”