Schories, D, Anibal, J, Chapman, AS, Herre, E, Isaksson, I, Lillebø, AI, Pihl, L, Reise, K, Sprung, M and Thiel, M (2000) Flagging greens:hydrobiid snails as substrata for the development of green algal mats (Enteromorpha spp.) on tidal flats of North Atlantic coasts. Marine Ecology Progress Series, 199 . pp. 127-136. DOI https://doi.org/10.3354/meps199127.

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Abstract

During the past 3 decades, dense mats of green algae (especially Enteromorpha spp.) have been recorded regularly from tidal flats worldwide. The development of green algal mats on tidal flats may be initiated by overwintering and regrowthof adult plants or by the formation and release of small propagules, i.e. vegetative fragments, zoospores and zygotes. On soft sediments, macroinvertebrates may constitute prime substrata for germination of algal spores. Hydrobiid (mud-) snails arewidespread along North Atlantic soft sediment shores and were identified previously as important substrata for Enteromorpha spp. germlings in 1 of our study areas. To test the generality of this phenomenon, we investigated the presence ofEnteromorpha spp. germlings attached to hydrobiid snails from November 1995 to December 1996 on 6 tidal flats of North Atlantic coasts (Trälebergskile, Sweden; Königshafen Bay, Germany; Mondego Estuary, Portugal; Ria Formosa, Portugal; ColeHarbour, Nova Scotia, Canada; Lowes Cove, Maine, USA). With 1 exception, hydrobiid snails were present in all areas studied, and intensive growth of Enteromorpha spp. occurred during summer. Throughout winter 1995/96, hardly any Enteromorphaspp. germlings were found on snail shells, but over the following months germlings developed on up to 60% of the hydrobiid snails present. In 2 areas (Königshafen, Germany; Lowes Cove, USA), germling abundance on hydrobiids began to rise before the peakof green algal mat development. In Trälebergskile, Sweden, high mat abundance occurred simultaneous to and after increased germling abundance on Hydrobia ulvae. Densities of snails were very low, however, and hydrobiids appeared to beunimportant as substratum. No clear temporal pattern between high germling abundance on snails followed by mat development was found in the other 3 study areas (Ria Formosa, Portugal; Mondego Estuary, Portugal; Cole Harbour, Canada). In Lowes Cove, USA,germlings and juveniles of Enteromorpha spp. first grew at the site with high Hydrobia abundance and were subsequently drifted to another site where they developed into full mats. We conclude that initiation of green algal mats bygermination on Hydrobia spp. may be a general phenomenon, but that other modes of development also occur frequently. Pelagic drift of overwintering thalli to new sites, followed by prolific growth, might be of similar or greater importance.

Document Type:	Article
Programme Area:	PA Not Applicable
Research affiliation:
Refereed:	Yes
Open Access Journal?:	No
DOI:	https://doi.org/10.3354/meps199127
ISSN:	0171-8630
Date Deposited:	05 Nov 2025 11:59
Last Modified:	05 Nov 2025 11:59
URI:	https://cris.leibniz-zmt.de/id/eprint/5951

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