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Chapter 2 - Coastal Ecosystemslands to migrate slowly southward (westward on LongIsland), with sand lost from the north (east) end oftentransported to build new beaches and dunes at the south(west) end. Hurricanes and nor’easters episodically movetremendous quantities of sand, both onshore and offshore,as well as along the main axis of the islands. Barrierbeaches typically protect tidal lagoons, coastal salt ponds,or salt marshes behind them. Breaches or blowouts of thebeach/dune systems can occur during major storms, creatingnew channels for flow between the ocean and backbays, and flood plain deltas which eventually submerge tocreate sand flats, or become vegetated to create wetlands.In the more northern part of the region sandy beachestend to be pocket beaches at the head of small bays orfringing beaches at the base of bluffs. These are muchsmaller than barrier beaches but cumulatively still figurein the overall sediment budget and habitat dynamics ofestuaries.All types of sandy beaches in this region are breedinggrounds for endangered and threatened species such as thepiping plover, least terns, Arctic terns, roseate terns as wellas several species of sea turtles (see Chapter 11 and 12 formore information). They also provide critical roost sitesfor migrant shorebirds. The sand of an open beach mayappear relatively devoid of marine life, but a variety of specieslive in the sand as infauna, often serving as importantfood sources (Bertness 2006). The value of sandy beachesto marine species is enhanced by their functional relationshipto the habitats behind them (e.g. dune systems) andto the productive sand and mud flats (see below) often associatedwith them.Sandy ocean beaches have been long been valued for theirrecreation and tourism value and billions of dollars arespent to maintain these resources. This maintenancecan include artificial stabilization to minimize erosion.However, in some cases the very techniques designed tosecure the beach for human uses, such as groins, beachwalls, and beach fill, actually interfere with the dynamicsnecessary for sandy shorelines and barrier islands topersist. This is particularly relevant in the face of risingsea level and storm surges. Thus, these shoreline armoringmeasures are actually detrimental to the ecologicalcommunities that rely on the beaches and adjacenthabitats (Pilkey and Dixon 1996).Cobble ShoresCobble shores range from the mid to high energy cobblefillednooks among the rocky headlands to stretches ofcobble-lined shoreline adjacent to sandy beaches. Morecommon in the northern half of the region, they supporta different suite of species than the rocky headlands, asthe cobble provides a less stable substrate for attachment.Cobble stones roll about in the surf, and are shoved intopiles during one storm event and spread out again in another.Species associated with the cobble shore tend to besmall, mobile, and short-lived (Tyrrell 2005), commonlyincluding Irish moss, barnacles, periwinkles, and otherinvertebrates and the shorebird species that feed on them.The large algae species of the rocky headlands are mostlyabsent here but may be present on larger boulders.Sand and Mud FlatsNon-vegetated sheltered coasts, usually sand and mudflats, have received less attention by resource managersthan sandy ocean beaches or vegetated tidal wetlands, andtherefore their importance to wildlife and humans hasoften been overlooked. Recently, however, the focus onthe relationship between endangered shorebirds and shelteredbeach-nesting horseshoe crabs has brought to lightthe ecological importance of these often under-protectedcoastlines. Intertidal sand and mud flats of the shelteredcoasts can be fringing or expansive, depending on bathymetryand tidal amplitude.Sediment size, sediment chemistry, inundation cycle,salinity, frequency of disturbance, and latitude are alldeterminants of the biotic community within flats. Theseflats are habitat for shellfish such as blue mussel (Mytilusedulis), Eastern oyster (Crassostrea virginica), hard clam(Mercenaria mercenaria) and soft shell clam (Mya arenaria).In addition to the typical resident invertebrate communitiesof annelids, crustaceans, and bivalves, tidal flats areforaging grounds for marine organisms such as eels, crabs,2-14Northwest Atlantic Marine Ecoregional Assessment • Phase 1 Report