Hypotheses
-
Local
shoreline productivity (growth rates of both plants
and animals) is closely linked in space and time
with food supply rather than with other factors
such as temperature.
Methods:
a ) measure growth rates of oysters, barnacles, and seaweeds through the
year at 9 sites (see Map) (link to Stuff on the Beach, etc).
b) measure food (chlorophyll and total suspended solids) in the water near
each beach during each sampling interval.
c) twice a year, measure stable isotope ratios of transplanted
oysters, thus gaining information on their sources of food (e.g.
from plankton versus river-supplied organic matter).
Link
to Findings
Sites
with higher shoreline productivity have higher
species diversity and higher biomass of organisms.
Methods:
a) quantify productivity using the methods above.
b) Measure species diversity at each beach once per year with an intensive
sampling program looking at both surface plants and animals, and species
living in the sediment.
c) Measure biomass of all organisms from random samples
on each beach.
Link
to Findings
- Sites
with higher rates of recruitment, i.e. colonization
of the shoreline by larvae and spores of marine
animals and plants, have higher diversity.
Methods:
a) quantify recruitment of surface-dwelling species (both
seaweeds and sessile animals) with ceramic settling tiles,
replaced monthly to measure the species arriving at different
times of year and at different locations.
b) quantify recruitment of species living in the sediment (worms and
clams) using cores of sterile sediment placed in the beach once a month.
- Sites
with more fine sediments (i.e. more sand and
mud, fewer pebbles and cobbles) increase recruitment
of organisms that live in sediment but reduce
recruitment of surface species.
Methods:
a) quantify recruitment of species into sediment cores with varying
amounts of fine sediments included.
b) measure recruitment onto ceramic tiles in areas of different natural
abundances of fine sediments.
Link
to Findings
- Predation by a variety of consumers, especially
crabs and fishes, is higher at the south sites
than the north, reducing both diversity and abundance
of clams that recruit to these beaches. This predation
in the south is severe enough to result in few
clams (and other infauna) surviving for as long
as a year.
Methods:
a) quantify
predation on species living in the sediment (clams)
using cores of sterile sediment placed
in the beach from May through September.
Link
to Findings
- Relatively subtle increases in physical stresses,
especially from higher temperatures and lower salinities,
reduce survival of newly recruited organisms on
the southern beaches, resulting in lower diversity
and biomass of organisms there.
Methods:
a) measure temperatures on the beach
continuously using dataloggers.
b) measure nearshore water temperature and salinity every 1-2 months from a
boat 5m off shore using YSI Salinity, Conductivity Temperature meter.
c) measure porewater temperature and salintiy in randomly selected holes
at each site once a year.
Note: We have not performed physiological experiments on survival of young
clams under different physically stressful regimes; this research will necessitate
detailed lab experiments. Rather, we correlated differences in survival and
growth of clams among beaches with physical differences among beaches, and
also studied the timing of loss of young recruits (e.g. over the course of
the summer, in the predation experiment).
Link
to Findings
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