European intertidal marshes: a review of their habitat functioning and value for aquatic organisms

Abstract

Salt marshes form true ecotones between land and sea fauna and flora that have adapted to an environment that is both aquatic and terrestrial in nature. Despite the extreme and sharp gradients that exist in salt marshes, they form the temporary or permanent home for many animals and plants and they fulfil many important roles in marine and estuarine ecosystems. While research on the terrestrial component of European marshes has helped in their management, knowledge of the aquatic component has largely been ignored in safeguarding the existence and ecological importance of tidal marshes. This situation is in sharp contrast with studies of coastal marshes along the eastern and southeastern coasts of North America. The typical European salt marsh differs in several physical aspects from the typical American salt marsh, but recent investigations have indicated parallels regarding nekton habitat usage. The present paper reviews the current state of European studies on the habitat role that tidal marshes play for fish and crustacean fauna. Mirrored against the more extensive American literature, we discuss where functional similarities and differences exist between both types of tidal marshes and where further knowledge is still needed for European marshes. Management of European tidal marshes would benefit from extending the current knowledge, and this paper identifies potential topics of interest. KEY WORDS: European tidal marsh · Estuarine systems · Nekton · Habitat functioningResale or republication not permitted without written consent of the publisher

Habitat connectivity and spatial complexity differentially affect mangrove and salt marsh fish assemblages

“…According to Hutchinson (1953), low complexity landscapes with fewer niches will result in fewer habitat specialists. Only 1 fish species (the common goby Pomatoschistus microps) could be considered a habitat specialist in the European salt marsh, with the other fish species found in salt marshes also present in the adjacent sublittoral habitats (Mathieson et al 2000, Cattrijsse & Hampel 2006. In contrast, the tropical coastal seascape has many specialist fish species associated with individual patch types along the topographically complex mangrove−seagrass−reef continuum (Gratwicke & Speight 2005, Wilson et al 2008.…”

“…Indo-Pacific mangroves and European salt marshes are important nursery sites, where adult and larval fish and crustaceans migrate into the habitat on the flood tide to feed and to shelter from predators between the mangrove roots, or in the shallow salt marsh channels (Beck et al 2001, Cattrijsse & Hampel 2006, Faunce & Serafy 2006. Fish return to the adjacent intertidal mudflats and subtidal channels (for salt marshes) or to adjacent seagrass beds and coral reef flats (for mangroves) on the ebb tide.…”

“…Whilst IndoPacific mangrove flora is characterised by halophytic trees, European salt marsh is characterised by a heterogeneous halophytic grass, herb and shrub community. Both habitats are similarly characterised by widely fluctuating environmental factors, such as temperature, salinity and currents (Cattrijsse & Hampel 2006, Nagelkerken et al 2008. It is important to clarify the differences in tidal regime between IndoPacific (mesotidal) and Caribbean/Meso-American (Gulf of Mexico) mangroves (microtidal), and between US Atlantic (mesotidal, dominated by Spartina alterniflora, vegetation flooded on every tide) and European (macrotidal, diverse community of halophytes, vegetation flooded only on spring tides) salt marshes (Sheaves 2005, Cattrijsse & Hampel 2006, Unsworth et al 2007a.…”

“…Our study was designed to determine the extent to which patch structural complexity, habitat complexity, structural connectivity or a combination of these variables influence fish species richness and population density in temperate salt marshes and tropical mangroves, 2 vegetated coastal habitats that are both considered to provide increased shelter, food and a nursery function to fish (Beck et al 2001, Cattrijsse & Hampel 2006, Nagelkerken et al 2008. The purpose of the study was to identify and compare the relative importance of differing seascape and environmental variables across multiple spatial scales in influencing fish assemblage density and richness between these 2 important habitats.…”

Fish assemblages of shallow intertidal habitats of the Ria Formosa lagoon (South Portugal): influence of habitat and season

“…In general, fish assemblages within intertidal marsh areas are formed mainly by estuarine resident and marine migrant species, with an important presence of juvenile fish, revealing that marshes may play a relevant role as nursery grounds. Comparative studies showed that fish communities associated with seagrass and unvegetated creeks within intertidal marsh areas were structurally different, with unvegetated habitats dominated by relatively few species.In Europe most studies on intertidal marsh habitats concern unvegetated creeks and mud flats (Drake & Arias 1991a, Cattrijsse et al 1994, Laffaille et al 2000, Mathieson et al 2000, Salgado et al 2004a, Veiga et al 2006, with no research on the differences between fish assemblages in intertidal seagrass beds and unvegetated creeks (Cattrijsse & Hampel 2006). In order to understand the role of these 2 shallow intertidal habitats in the overall ecology of the European saltmarshes, it is crucial to know if they are utilized by different ichthyofaunal communities.…”