Impact of habitat edges on density and secondary production of seagrass-associated fauna

Hydrodynamics of model Posidonia oceanica patches in shallow water

“…This would alter rates of pollen interception by seagrass carpels (Ackerman 2002) and would reduce the rates of deposition of bivalves and other pelagic larvae (Irlandi et al 1999;Crimaldi et al 2002). This implies that these ''in-wake'' patches would have sparser populations of adult bivalves and other fauna such as gastropods and polychaetes than homogeneous meadows (Bologna and Heck 2002). The high Reynolds stress values found in the wakes imply that organic (and mineral) particulates carried in them may readily be exchanged into the rapid overflow and thus have a greater likelihood of traveling beyond inwake patches.…”

“…This research has found that patch size and isolation (e.g., BarberaCebrian et al 2002;Hovel 2003), structural complexity in terms of shoot and biomass density (e.g., Irlandi 1997;Hovel 2003), and patch shape and orientation (Tanner 2003) are more important for determining faunal abundances and species richness than simply the areal extent of seagrass habitat. Patch edges have also been found to be particularly important in this respect: Faunal abundances have been found to be significantly higher at edge sites than in patch interiors or on bare substrate (e.g., Barbera-Cebrian et al 2002;Bologna and Heck 2002). The present work shows, for the first time, the similar importance of patch-scale parameters (in particular patch isolation) on the hydrodynamics, thus providing a basis upon which ecohydrodynamic interactions at this scale can be investigated.…”

“…The degree of patchiness is positively correlated with current velocity (Fonseca et al 1983)-possibly because flow acceleration around patches causes local erosion, thus sustaining their isolation (Gambi et al 1990)-and the spatial distribution of patches profoundly affects the flow field around them (Granata et al 2001). Patch size and distribution are also important in determining the distribution of seagrass-associated fauna (e.g., Irlandi 1997;Bologna and Heck 2002;Tanner 2003). Flow conditions are important determinants of the meadow-scale morphodynamics of fragmented seagrass communities (Fonseca and Bell 1998).…”

Abrupt transitions between macrobenthic faunal assemblages across seagrass bed margins

“…Little previous work has concerned small, 12 fragile, epibenthic microgastropods such as Calopia and Pseudoliotia -13 forms that dominate the Stradbroke seagrass patches away from edges 14 (Barnes andBarnes, 2011, 2012;Barnes and Ellwood, 2012). But as water 15 velocities are known to be higher near seagrass margins (Peterson et al, 16 2004;Murphy et al, 2010), it is perhaps not surprising that some species, 17 such as Pseudoliotia, should be less abundant and widespread under the 18 more turbulent conditions near the interface, maybe via effects on their 19 recruitment (Bologna and Heck, 2002;Matias et al, 2013) or because of 20 dislodgement (Tuya et al, 2011). In addition, small, fragile animals may be 21 at greater risk from predators when relatively exposed (Kark and van 22 Rensburg, 2006;Barnes, 2010).…”

How lonely they are? A degree of isolation among macrozoobenthos species in the Marine Protected Area, the Bay of Puck, the Southern Baltic

“…At the same time, the number of species and general benthic biomass increased (Osowiecki 2000), which might be a positive effect of habitat fragmentation. In shallow water, the number of small vegetation patches (a larger edge/center ratio) may efficiently attenuate the water flow, catch sediment and affect the larval settlement better than a single large patch (Bologna and Heck 2002). Certain taxa show affinity to small, isolated patches of seagrass (Healey and Hovel 2004), hence patchy, mosaic habitats are often richer compared to contiguous ones (Roberts and Poore 2005).…”