Effects ofFucus vesiculosus covering intertidal mussel beds in the Wadden Sea

Abstract

The brown alga Fucus vesiculosus forma mytili (Nienburg) Nienhuis covered about 70 % of mussel bed (Mytilus edulis) surface area in the lower intertidal zone of K6nigshafen, a sheltered sandy bay near the island of Sylt in the North Sea. Mean biomass in dense patches was 584 g ash-free dry weight m -2 in summer. On experimental mussel beds, fucoid cover enhanced mud accumulation and decreased mussel density. The position of mussels underneath algal canopy was mainly endobenthic (87 % of mussels with > 1~ of shell sunk into mud). In the absence of fucoids, mussels generated epibenthic garlands (81% of mussels with < I/3 of shell buried in mud). Mussel density underneath fucoid cover was 40 to 73 % of mussel density without algae. On natural beds, barnacles (Balanidae), periwinkles (IAttorina littorea) and crabs (particularly juveniles of Carcinus maenas) were significantly less abundant in the presence of fucoids, presumably because most of the mussels were covered with sediment, whereas in the absence of fucoids, epibenthic mussel clumps provided substratum as well as interstitial hiding places. The endobenthic macrofauna showed tittle difference between covered and uncovered mussel beds. On the other hand, grazing herbivoresthe flat periwinkle LittoHna mariae, the isopod Jaera albi[rons and the amphipods Gammarus spp. -were more abundant at equivalent sites with fucoid cover. The patchy growth of Fucus vesiculosus on mussel beds in the intertidal Wadden Sea affects mussels and their epibionts negatively, but supports various herbivores and increases overall benthic diversity.

Recovery of the brown alga Fucus gardneri following a range of removal intensities

“…However, Fucus germlings were no more or less abundant in open areas over the course of our experiment. Canopy-forming algae have also been shown to enhance (McCook and Chapman, 1991;Albrecht and Reise, 1994) or suppress (Dethier and Duggins, 1988) herbivore abundance, and thus may indirectly influence recovery rates, but herbivore abundances in our experiment did not differ between treatments. Similarly, the removal of Fucus canopies often leads to blooms of other algal species (Southward and Southward, 1978;van Tamelen et al, 1997), which may suppress recovery.…”

How an introduced seaweed can affect epibiota diversity in different coastal systems

“…F. vesiculosus in this habitat lacks a holdfast and is, instead, permanently attached to the bivalve bed by mussel byssus threads. It may cover up to 70% mussel bed surface area (Albrecht and Reise 1994). This specific form of bladder wrack was first described as Fucus mytili (Nienburg 1925(Nienburg , 1927 and is now referred to as F. vesiculosus forma mytili (Nienburg 1925;Albrecht 1998).…”

Subtidal and intertidal mussel beds (Mytilus edulis L.) in the Wadden Sea: diversity differences of associated epifauna

“…Site A was subject to the strongest waves and tidal currents whilst sites B (close to the main tidal channel) and C were more sheltered within 'Königshafen' bight (Behrens et al 1996). Patches of mussel beds colonized by the seaweed Fucus vesiculosus f. mytili (Nienburg) harbour a specific faunal assemblage (Albrecht and Reise 1994) and, since these patches only occurred intertidally, they were excluded from this investigation. The same applies to tide pools.…”

“…Dittmann 1990;Obert and Michaelis 1991;Albrecht and Reise 1994;Günther 1996;Albrecht 1998) or subtidal mussel beds (e.g. Dekker 1989;Dankers and Zuidema 1995).…”