Matthew D. Cacopardo
Rocky Intertidal
There are several dominant shoreline habitats found throughout the harbor and the surrounding shoreline. These include rocky shores, soft sediment beaches and salt marshes. This study will be conducted on intertidal zone at each location. The intertidal or littoral zone comprises the area of extreme low tide to extreme high tide. It is important that the teacher checks the time of low tide for the day of sampling because this is the time for most effective sampling.
Rocky shores are wonderful places to find many sessile and slow moving invertebrates along with hardy algae that are able to deal with constant fluctuating physical environments. These environments are usually abundant with species due to the plankton rich water. This water is constantly replenished due to a diurnal (twice a day) tidal cycle.
Rocky intertidal algae range from microscopic diatoms to large seaweeds and kelp. These plants do well in the areas due to the abundant nutrient rich water. These nutrients come from terrestrial runoff and from the rise of deeper oceanic currents. Major seaweeds include green, brown and red algae. Phytoplankton is also found in great abundance. (see Activity).
Rocky intertidal herbivores include sessile filter feeders and slow moving resident grazers that have modified mouth parts for scraping hard surfaces and slicing tissue from macroalgea. Common grazers include periwinkles
Littorina littorina
, limpets
Acmaea testudinalis
, amphipods and isopod crustaceans. Due to high levels of pelagic microorganisms, phytoplankton, Cyanobacteria and zooplankton are abundant food sources for sessile filter feeders. Typical sessile filter feeders that students will find are ribbed mussels, blue mussels
Mytilis edulis
, and barnacles (Bertness. 1999.).
Predation on rocky shores is rampant with such an abundance of species. This predation causes some of the most unique invertebrate species in search of a tasty treat. Shell drilling snails, starfish and crabs rely on this productive environment. Species that may be found are:
Dog Welks
Nucella lapillus
,
Oyster Drills
Uroslapiny cinera
,
Starefish
Asterias
,
European Green Crabs
Carcinus maenas
,
Japanese Shore Crabs
Hemigrapus sanguinis
,
Blue Crabs
Callenecties sapidus
.
Tidal Flats
The east coast has been geologically stable for the past 150 years. Throughout this time erosional sediments have accumulated along this coastline which has left sandy or muddy shores. These soft sediment habitats are sheltered from waves. At first sight they may appear to be a barren scene but they are actually biologically rich. Because of the stability of the habitat they can host a diverse assemblage of organisms. Tidal flats contain sediments that range form fine mud 0.05mm in diameter to coarse sand 1.0 mm in diameter. Sediment sizes on tidal flats generally increase with increasing intertidal height. The softer sediment is home to bacterial and protozoan which are feed on by burrowing worms and bivalves which are caught by crabs. These benthic food chains rely heavily on the water column supply of clean water filled with primary producing plankton and detritus. Typical organisms that will be found in these environments include filter feeders, deposit feeders and predators.
Filter Feeders include
Surf Clam
Mulinia lateralis
Razor Clam
Ensis
Quahog
Mercenaria mercenaria
Blue Mussel
Mytilis edulis
Ribbed Mussel
Geukensia demissa
Deposit feeders are among the most diverse species found in the tidal flats. Members of many taxonomic groups which include worms, amphipods and shrimp, sea cucumbers clams and snails survive by extracting detritus and organic material from the tidal flat sediments. These organisms are important in food chains by converting detritus into microorganisms biomass for higher trophic levels as well as biotubators which resuspend substrate into the water column.
Deposit Filter Feeders include
Mud Snails
Fiddler Crabs
Spaghetti worms
Amphitrite
Bamboo Worms
Lugworm
Predators include crabs. The dominant predator in these environments is the blue crab. Blue crabs are quite vicious and should only be collected if a shell remain is found. (Bertness. 1999.).
