268
J.R. Cantera and J.F. Blanco
18.3 Coastal Habitats and Communities
A combination of recent geological activity, wide tidal range, high precipitation, and elevated sediment input by rivers has bestowed Buenaventura
Bay with a variety of habitats, like depositional intertidal sand beaches and
mud flats, intertidal cliffs and rocky shores, mangrove swamps, and the
pelagic zone of the estuary (Fig. 18.1 ).
18.3.1 Sandy Beaches
The discharge of sand by rivers and sediments from coastal erosion have
formed sandy beaches at the mouth of Buenaventura Bay and shoals and
sandy bars parallel to the coast (Fig. 18.1). The sandbars prevent shore erosion and some have developed into barrier islands (i.e. Soldado Island)
occupied by beach vegetation and mangroves (Martinez et al. 1995). The
morphodynamics of shoals and sand beaches are largely controlled by
tidal currents and wave overwash during spring tides and ENSO events
(Gonzalez et al. 1998) when large amounts of sand are deposited (Cantera
199l).Apart from the obvious action of tides and waves, the nature of sediments, soil humidity gradients, dissolved oxygen content and salinity of
interstitial water, sand surface temperatures, and light penetration into
sediments (2-10 em) also determine the composition and distribution of
species on beaches (Cantera et al. 1992). The abundance and diversity of
species on sandy beaches is low and most organisms are infaunal, though
shore and marine birds are constant visitors.
The upper littoral zone of sandy beaches is occupied by plants ( Cenchrus paucijlorus, Homolepis aturensis, Ipomoea pes-caprae, I. stolonifera,
Canavalia maritima, Pectis arenaria, Stenotaphrum secundatum) which
have a stabilizing effect on the substrate. Insects ( diptera, coleoptera,
orthoptera) are abundant. Although the hermit crab Coenobita compressus
accounts for 59 o/o of the marine invertebrates in this zone, ghost crabs
(Ocypode gaudichaudii, 0. occidentalis), that move over the beach in large
groups at low tide, are the most conspicuous organisms. Insects (collembola, diptera) and crustaceans (amphipods, isopods) are found under tidal
litter accumulations, with high densities ( > 1,000 in d. m- 2 ) of the amp hi pod
Talitrus sp. The intertidal zone is occupied by the suspension-feeding clam
Donax assimilis (17.6 in d. m- 2 ) , olives ( Olivella sp.; 34.3 ind. m- 2 ), and sand
crustaceans (Emerita rathbunae; 6 ind. m- 2 ), which follow the advance and
retreat of tides. Marine species, like annelid errant worms (Nereidae), tube
worms, bivalves (Iphigenia, Tellina, Sanguinolaria) , and seasonally abun-
J.R. Cantera and J.F. Blanco
18.3 Coastal Habitats and Communities
A combination of recent geological activity, wide tidal range, high precipitation, and elevated sediment input by rivers has bestowed Buenaventura
Bay with a variety of habitats, like depositional intertidal sand beaches and
mud flats, intertidal cliffs and rocky shores, mangrove swamps, and the
pelagic zone of the estuary (Fig. 18.1 ).
18.3.1 Sandy Beaches
The discharge of sand by rivers and sediments from coastal erosion have
formed sandy beaches at the mouth of Buenaventura Bay and shoals and
sandy bars parallel to the coast (Fig. 18.1). The sandbars prevent shore erosion and some have developed into barrier islands (i.e. Soldado Island)
occupied by beach vegetation and mangroves (Martinez et al. 1995). The
morphodynamics of shoals and sand beaches are largely controlled by
tidal currents and wave overwash during spring tides and ENSO events
(Gonzalez et al. 1998) when large amounts of sand are deposited (Cantera
199l).Apart from the obvious action of tides and waves, the nature of sediments, soil humidity gradients, dissolved oxygen content and salinity of
interstitial water, sand surface temperatures, and light penetration into
sediments (2-10 em) also determine the composition and distribution of
species on beaches (Cantera et al. 1992). The abundance and diversity of
species on sandy beaches is low and most organisms are infaunal, though
shore and marine birds are constant visitors.
The upper littoral zone of sandy beaches is occupied by plants ( Cenchrus paucijlorus, Homolepis aturensis, Ipomoea pes-caprae, I. stolonifera,
Canavalia maritima, Pectis arenaria, Stenotaphrum secundatum) which
have a stabilizing effect on the substrate. Insects ( diptera, coleoptera,
orthoptera) are abundant. Although the hermit crab Coenobita compressus
accounts for 59 o/o of the marine invertebrates in this zone, ghost crabs
(Ocypode gaudichaudii, 0. occidentalis), that move over the beach in large
groups at low tide, are the most conspicuous organisms. Insects (collembola, diptera) and crustaceans (amphipods, isopods) are found under tidal
litter accumulations, with high densities ( > 1,000 in d. m- 2 ) of the amp hi pod
Talitrus sp. The intertidal zone is occupied by the suspension-feeding clam
Donax assimilis (17.6 in d. m- 2 ) , olives ( Olivella sp.; 34.3 ind. m- 2 ), and sand
crustaceans (Emerita rathbunae; 6 ind. m- 2 ), which follow the advance and
retreat of tides. Marine species, like annelid errant worms (Nereidae), tube
worms, bivalves (Iphigenia, Tellina, Sanguinolaria) , and seasonally abun-