WHAT LIVES ON A WIND-TIDAL FLAT?
casual observer would quickly conclude that wind-tidal flats are devoid
of life. Irregular flooding,
hot summer temperatures, little freshwater inflow, and salty soils donít
allow typical marsh plant communities to develop.
Although not found on all wind-tidal flats, felt-like mats (Fig.
5) of microscopic, one-celled, blue-green algae (Cyanobacteria)
behave like plant communities, that is, they convert sunlight into energy
that can be used by other organisms (photosynthesis;
Flats that are frequently flooded are important biomass conversion sites, that is, areas where primary production is converted into animal biomass for use by higher-level consumers. Although some primary production is directly consumed, much of it enters the food chain as detritus. Many invertebrates live on the surface of the flats (epibenthic) or within the substrate (benthic or infauna) and are the primary consumers on wind-tidal flats (Fig. 6).
aquatic and semi-aquatic benthic organisms are found in the wet areas
of tidal flats. At the interface
between the flat and the adjacent bay where there is little chance of
drying out, polychaetes,
are the most common organisms. Sometimes
are found deep in the sediments, but they are not very common.
In wet areas at slightly higher elevations, fly
larvae are the most common organisms.
In the higher, drier areas of tidal flats, salt-water adapted insects
like rove beetles (Family
Staphylinidae) that live on the surface are the only invertebrates
able to survive.
fish such as sheepshead
minnows may be found on wind-tidal flats when they are flooded, shorebirds
that use exposed flats as foraging habitat
are the most important vertebrate organisms
found on tidal flats. Wind-tidal
flats in the Laguna Madre are one of the most significant feeding areas
for shorebirds on the Texas Gulf Coast.
At least 26 species of shorebirds
have been reported on wind-tidal flats in the Coastal Bend.
Several shorebird feeding guilds
can be found. Shorebirds
such as plovers find their food using their eyes.
They see their prey or some evidence of the prey, like a burrow
entrance, then use their bills to capture it.
Other shorebirds like sandpipers and dowitchers find food by probing
into the substrate and feeling their prey with special cells (Herbst
corpuscles) at the end of their bills.
These organs cause the bill to open and the prey is captured.
The prey that shorebirds capture is determined by the length of
their bill and their feeding strategy (Fig. 7).