3 Suspension Feeders on Sandy Beaches
E. JARAMILLO and M. LASTRA
3.1 Introduction
Sandy beaches are the most common coastal habitat on temperate and
tropical coasts; comprising about 75 % of the world's coastal zone (Bascom
1980). Exposed sandy beaches support a diverse and abundant macroinfauna
(Brown and McLachlan 1990). In terms of species richness, sandy beach
macroinfauna is dominated by crustaceans, bivalves and polychaetes. In
terms of abundance, peracarid crustaceans are usually the dominant organisms. However, large suspension feeders, such as anomuran decapods
(Emerita spp.) and bivalves (Mesodesma and Donax spp.), are usually the top
contributors to biomass (e.g. Hutchings et al. 1983; Donn 1990; Dugan et al.
1994; Jaramillo et al. 2001).
Basically, sandy beaches can be described in terms of wave and sediment
characteristics, also called beach morpho dynamics. A dimensionless index,
Dean's parameter (also called parameter D), reflects the interaction between
wave height, wave period and sediment fall velocity of sand particles from the
sediments at the breaker zone (Short and Wright 1983; Short 1996); i.e.
D=Hb/T x sand fall velocity, where Hb is the height in centimeters of waves at
the breaker zone, T is the wave period in seconds, while sand fall velocity
(cm S-i) is derived from the mean grain size of sands from the breaker zone
and empirical data given by Gibbs et al. (1971). Using this parameter, three
major types of beaches can be described: reflective, intermediate and dissipative.
Reflective beaches are characterized by a virtual absence of surf zone,
coarse sand, small waves (usually lower than 1 m) and steep profiles. At the
other end of the spectrum, dissipative beaches have a wide surf zone (i. e.,
waves dissipate most of their energy before reaching the beach face), fine
sands, large waves (usually higher than 2 m) and flat profiles. Intermediate
beaches lie between both extremes, with bar-trough systems, rip currents and
variable seasonal conditions (Short and Wright 1983; Short 1996). The swash
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001
E. JARAMILLO and M. LASTRA
3.1 Introduction
Sandy beaches are the most common coastal habitat on temperate and
tropical coasts; comprising about 75 % of the world's coastal zone (Bascom
1980). Exposed sandy beaches support a diverse and abundant macroinfauna
(Brown and McLachlan 1990). In terms of species richness, sandy beach
macroinfauna is dominated by crustaceans, bivalves and polychaetes. In
terms of abundance, peracarid crustaceans are usually the dominant organisms. However, large suspension feeders, such as anomuran decapods
(Emerita spp.) and bivalves (Mesodesma and Donax spp.), are usually the top
contributors to biomass (e.g. Hutchings et al. 1983; Donn 1990; Dugan et al.
1994; Jaramillo et al. 2001).
Basically, sandy beaches can be described in terms of wave and sediment
characteristics, also called beach morpho dynamics. A dimensionless index,
Dean's parameter (also called parameter D), reflects the interaction between
wave height, wave period and sediment fall velocity of sand particles from the
sediments at the breaker zone (Short and Wright 1983; Short 1996); i.e.
D=Hb/T x sand fall velocity, where Hb is the height in centimeters of waves at
the breaker zone, T is the wave period in seconds, while sand fall velocity
(cm S-i) is derived from the mean grain size of sands from the breaker zone
and empirical data given by Gibbs et al. (1971). Using this parameter, three
major types of beaches can be described: reflective, intermediate and dissipative.
Reflective beaches are characterized by a virtual absence of surf zone,
coarse sand, small waves (usually lower than 1 m) and steep profiles. At the
other end of the spectrum, dissipative beaches have a wide surf zone (i. e.,
waves dissipate most of their energy before reaching the beach face), fine
sands, large waves (usually higher than 2 m) and flat profiles. Intermediate
beaches lie between both extremes, with bar-trough systems, rip currents and
variable seasonal conditions (Short and Wright 1983; Short 1996). The swash
Ecological Studies, Vol. 151
K. Reise (ed.) Ecological Comparisons
of Sedimentary Shores
© Springer-Verlag Berlin Heidelberg 2001