Consequences of ecological connectivity: the coastal ecosystem mosaic

Abstract

Connectivity links habitats in space and time. It is a key process that facilitates many life-history functions of myriad species in a variety of contexts over a wide range of scales. Perhaps its most obvious application is to the multifaceted linkages among the diverse habitat units comprising ecosystem complexes like the coastal ecosystem mosaic (CEM) -the tightly interlinked coastal, estuarine, wetland and freshwater habitats at the interface of land and sea. The ability to utilise this diversity of connected habitats is integral to the life histories of a broad spectrum of organisms, with connectivity between habitats being crucial to important functions like nursery utilisation. Although connectivity is an obvious feature of the CEM, investigation of its implications has largely been restricted to the migration of organisms. However, connectivity has much broader conceptual relevance. It is a pervasive and multifaceted process affecting and enabling the lives of organisms over the full range of conceptual scales, with ecosystem components connected by a diversity of factors, including physical and biological translocation of nutrients, ontogenetic, life history, spawning and feeding migrations, food-web dynamics, predator-prey interactions, and many more. All of these play crucial roles in structuring biological populations, communities and assemblages, and in driving the biological processes that support them. Moreover, connectivity is a prominent and necessary component of ecological concepts, ranging from estuarine dependence and metapopulation dynamics to foraging arena theory. Considering connectivity as a multifaceted process leads to specific hypotheses about the functioning of the CEM and similar ecosystem complexes. KEY WORDS: Connectivity · Coastal ecosystems · Estuarine · Wetland · Ecosystem interactionsResale or republication not permitted without written consent of the publisher

Estuarine consumers utilize marine, estuarine and terrestrial organic matter and provide connectivity among these food webs

“…Connectivity between habitats is facilitated by physical exchanges of water and movements or migrations of animals (Vanni et al 2004, Sheaves 2009, Hoffman et al 2015. The cross-habitat movements of nutrients and organic matter (OM) can influence food web dynamics and productivity in the recipient estuarine habitat (Nixon & Buckley 2002, Riley et al 2004).…”

Effects of Slotted Water Control Structures on Nekton Movement within Salt Marshes

“…The congregating nekton was much more abundant (3-6£) at the WCSs than at the salt-marsh creek site even though the assemblages were similar in species composition, dominant species, and individual sizes. High nekton densities at WCSs may indicate ecological hot spots at these critical bottlenecks, where processes such as predation and foraging are enhanced or intensified relative to those in other habitats within the estuary (Sheaves 2009). This concept has already been advanced for structures (e.g., dams) in riverine ecosystems (McLaughlin et al 2013) and is likely applicable for structures in estuarine ecosystems as well (Sheaves 2009).…”

“…High nekton densities at WCSs may indicate ecological hot spots at these critical bottlenecks, where processes such as predation and foraging are enhanced or intensified relative to those in other habitats within the estuary (Sheaves 2009). This concept has already been advanced for structures (e.g., dams) in riverine ecosystems (McLaughlin et al 2013) and is likely applicable for structures in estuarine ecosystems as well (Sheaves 2009). For some individuals, WCSs appear to be used primarily as a foraging site rather than as an access point for entering or exiting managed marshes, which may account for the low passage rates observed here and elsewhere (Kimball et al 2010).…”

“…Commonly used WCSs include fixed-crest or variable-crest weirs, gated types, and slotted types (Rogers et al 1994). By regulating water levels, structural marsh management can establish stable hydrological regimes in the managed area but also may restrict life history connectivity by impeding nekton movement (Rogers et al 1994;Secor and Rooker 2005;Sheaves 2009). Reduced access from WCSs for transient nekton that must migrate to estuarine nursery habitat from nearshore and offshore spawning areas could negatively affect their recruitment into salt marshes during early life history stages and could subsequently limit the emigration of older juveniles or adults to other coastal habitat types.…”

“…The value of these nurseries depends on the degree of hydrological connectivity with marine spawning areas (Rozas et al 2013) and the greater mosaic of integral habitats within coastal and estuarine ecosystems (Peterson 2003;Able 2005;Sheaves 2009). Nekton movement through this habitat mosaic-at both small and large spatial and temporal scales-provides an important pathway for the transfer of energy and nutrients among habitats (Kneib 2000;Allen et al 2013).…”