64
E. Jaramillo and M. Lastra
with published data from Australia (McLachlan et al. 1996) and Oman
(McLachlan et al. 1998). In the second part we also examine unpublished and
published information to examine whether morpho dynamic beach types
affect the population biology and behavior oflarge suspension feeders such as
Emerita and Donax. Finally, we analyze across- and along-shore zonation of
these suspension feeders to examine the possible role of biological interactions in shaping spatial distributions on exposed sandy beaches.
3.2 Beach Morphodynamic Types vs. Community Structure
of the Macroinfauna
E. analoga is the most common suspension feeder inhabiting sandy beaches
along the Chilean coast. It primarily occupies the lower shore levels (swashresurgence zone), although stranded animals are sometimes also found at the
mid-shore levels or retention zone. Along this coast, the abundance of this
species is usually higher than 50 %, while biomass values may well represent
more than 80 % of the whole macroinfauna (Fig. 3.3). The dominance of this
species results in significant correlations for total abundance and biomass vs.
abundance and biomass of E. analoga on these beaches (log total abundance =
-3.27 + 1.61 X log abundance of E. analoga, r=0.85, n= 19, p
22 out of 36 beaches surveyed along the coast of California (5 to 98 % of the
total macrofaunal abundance). Similarly, biomass of this crab accounted for
22-99 % of the total biomass on those beaches (Dugan et al. 2000).
The total abundance of the macroinfauna on Chilean beaches is higher
than the worldwide model presented by McLachlan et al. (1996) (Fig. 3.4); in
other words, similar abundances were found on Chilean beaches with lower
BSI values than those studied at other latitudes such as Australia, Spain and
Oman. Biomass vs. BSI shows a similar pattern to that of the abundance, and,
in some cases, macroinfaunal biomasses on Chilean beaches were higher than
those found on Omani beaches, being both similar in BSI (Fig. 3.4). We
conclude from this that for the sandy beaches of Chile and also those in
California (see Dugan and Hubbard 1996), factors other than beach morphodynamics influence patterns of macroinfaunal community structure in
exposed sandy beaches. Those factors would apply primarily to large suspension feeders such as E. analoga; e.g. upwelling waters along the coast of
Chile and California. Interestingly, sandy beaches located on coasts with upwelling waters (e.g., sandy beaches of Galicia, Spain; de la Huz 1999) but with
low abundances and biomass of large suspension feeders (or even absent)
E. Jaramillo and M. Lastra
with published data from Australia (McLachlan et al. 1996) and Oman
(McLachlan et al. 1998). In the second part we also examine unpublished and
published information to examine whether morpho dynamic beach types
affect the population biology and behavior oflarge suspension feeders such as
Emerita and Donax. Finally, we analyze across- and along-shore zonation of
these suspension feeders to examine the possible role of biological interactions in shaping spatial distributions on exposed sandy beaches.
3.2 Beach Morphodynamic Types vs. Community Structure
of the Macroinfauna
E. analoga is the most common suspension feeder inhabiting sandy beaches
along the Chilean coast. It primarily occupies the lower shore levels (swashresurgence zone), although stranded animals are sometimes also found at the
mid-shore levels or retention zone. Along this coast, the abundance of this
species is usually higher than 50 %, while biomass values may well represent
more than 80 % of the whole macroinfauna (Fig. 3.3). The dominance of this
species results in significant correlations for total abundance and biomass vs.
abundance and biomass of E. analoga on these beaches (log total abundance =
-3.27 + 1.61 X log abundance of E. analoga, r=0.85, n= 19, p
22 out of 36 beaches surveyed along the coast of California (5 to 98 % of the
total macrofaunal abundance). Similarly, biomass of this crab accounted for
22-99 % of the total biomass on those beaches (Dugan et al. 2000).
The total abundance of the macroinfauna on Chilean beaches is higher
than the worldwide model presented by McLachlan et al. (1996) (Fig. 3.4); in
other words, similar abundances were found on Chilean beaches with lower
BSI values than those studied at other latitudes such as Australia, Spain and
Oman. Biomass vs. BSI shows a similar pattern to that of the abundance, and,
in some cases, macroinfaunal biomasses on Chilean beaches were higher than
those found on Omani beaches, being both similar in BSI (Fig. 3.4). We
conclude from this that for the sandy beaches of Chile and also those in
California (see Dugan and Hubbard 1996), factors other than beach morphodynamics influence patterns of macroinfaunal community structure in
exposed sandy beaches. Those factors would apply primarily to large suspension feeders such as E. analoga; e.g. upwelling waters along the coast of
Chile and California. Interestingly, sandy beaches located on coasts with upwelling waters (e.g., sandy beaches of Galicia, Spain; de la Huz 1999) but with
low abundances and biomass of large suspension feeders (or even absent)