As a marine biologist for 30+ years, I've studied along beaches from Nova Scotia to the Bahamas. I still get to visit many beaches up and down the east coast (my son is a surfer, actually a very good surfer) as we travel for surf contests. As I walk along these beaches, I realize more and more, what a great beach that Tybee Island is for finding and seeing a large number of different marine animals. I don't know of any other east coast beach that can compare.
Tybee Island has an amazingly diverse collection of marine animals that can be seen by beachcombers, and especially by folks who learn where and how to look. Part of the reason that Tybee is so species rich is because of its location within a transition zone or "biogeographical province" between a cold-temperate fauna to our north and a tropical fauna to our south. Tybee gets some spill-over or overlap species that extend southward from Canada and beyond Cape Hatteras, NC, and some other species that extend northward from the Caribbean and beyond Cape Canaveral, FL. And what makes Tybee even more interesting is that many of these range extension animals come and go, depending on the season. During the winter, we get additional species that originated from the north; and during the summer, we get even more additional tropical and sub-tropical species that belong to the Caribbean assemblage. So what you find on Tybee's beach during one time of the year might well be different from what you find another time of the year. The result is that every trip to the beach at Tybee may well be different in regards to what you might see and find.
Another reason that Tybee has such a wide diversity and large number of different species along its beach is that there are a number of different habitats along the shore and close by. Tybee has its nice wide sandy beach habitats for animals that live in the sand and burrow through the sand; but it also has rock jetties that provide habitats for those animals that require a hard, non-moving surface for attachment. Close by are a large river inlet with its deep water habitats, and salt marshes with their tidal creeks. Just off shore are artificial and natural hard-bottom reefs. As beach visitors quickly realize, the range between high and low tide levels are large. In fact Tybee's tidal range is the largest along the east coast south of New England. So Tybee has a large intertidal zone, providing lots of space, especially for those animals that dwell in and burrow through the intertidal sand.
Just as bird watchers recognize Tybee as a prime location for spotting resident and migrating birds because of its location and the habitats it provides, marine biologists also consider Tybee Island as an interesting and species-rich area for study. While visiting Tybee Island, be sure to take the time to explore its beaches. There is a lot to be seen, found, and learned. And the best feature of exploring Tybee's beaches is that you never know what you might find, no matter how many times you go out.
COASTAL GEORGIA IS LOCATED IN THE MIDDLE OF AN OVERLAP AREA FOR COLD WATER AND TROPICAL SPECIES
| THE CAROLINIAN BIOGEOGRAPHICAL PROVINCE|
Tybee Island is located near the middle of the "Carolinian Biogeographical Province" that extends from Cape Hatteras, NC, to Cape Canaveral, FL.
This area is essentially an overlap area of two major "centers of distribution" for marine species:
1) a cold-temperate center along Canada
2) a tropical and sub-tropical center in the Caribbean Sea
As a result, some cold water species extend southward beyond Cape Hatteras NC, and some tropical species extend northward beyond Cape Canaveral FL.
By being located mid-way in this overlap zone, Tybee Island gets many of these species that extend from the north and from the south.
Added to this overlap are the appearance of additional seasonally occurring species. During the winter, some additional cold-water species move further south beyond NC and down along the GA coast. And during the summer, some additional tropical and sub-tropical species extend further north beyond Cape Canaveral FL, and up along the GA coast. Thus we get these additional temporary, seasonal species.
These seasonal additions to our coastal flora and fauna may be due to seasonal migrations (eg. by moving fish), but they
may also be due to seasonal life cycle and life history stages or phases (eg. by many of the seasonal seaweeds).
EXAMPLES OF SOME WINTER-TIME AND EARLY SPRING-TIME SPECIES ON TYBEE ISLAND
Winter and early spring seasonal species include some that appear due to life cycle stages, and others that appear along coastal Georgia due to migrations from the north and/or seasonal onshore-offshore migrations.
Lion's Mane Jellyfish Forbes' Sea Star Mushroom Jelly Red (Bangia) & Green (Enteromorpha)
EXAMPLES OF SOME SUMMER-TIME SPECIES ALONG TYBEE ISLAND AND COASTAL GEORGIA
Summer species include many migratory fish from the tropical and sub-tropical south, and warm-water invertebrates. Many of these summer species use the plankton rich waters of coastal GA to grow through the young stages of their life histories.
Bumper Sea Wasp Sargent Majors Young juvenile Snapper
Tarpon Sea Wasp Scars from a Sea Wasp Moon Jellyfish
Blue Crab Shrimp Baby Striped Burrfish
Other features, physical factors, and nearby habitats also contribute to the large species diversity of marine life that can be found along Tybee Island. These additional factors and features include:
- Large tidal range (distance between high and low tide)
- Coastal rivers, Savannah River Entrance
- Estuaries (where seawater and freshwater mix)
- Salt Marshes
- Rock Jetties
- Wide gradually sloping, sandy shoreline and beaches
- Offshore Reef and Hard Bottoms
Tides: Georgia has the largest tidal range (vertical distance between high tide and low tide) found anywhere on the east coast south of northern New England. As a result, we have large expanses of intertidal, soft bottom areas for diggers, burrowers, and tube dwellers.
Coastal Rivers, including the Savannah River: Coastal rivers (particularly the Savannah River adjacent to Tybee Island) provide a range of salinity variations and variety of habitats, including nearby deep-water areas. Rivers provide nutrients for phytoplankton, the base of many marine food chains and food for many filter-feeding animals.
Sturgeon are an ancient-looking fish, capable of living in the ocean as well as far up-river in major rivers, including the Savannah River.
Estuaries: Estuaries are partially-enclosed bodies of water where seawater and freshwater mix; and coastal Georgia has extensive estuaries in its coastal zone. Estuaries provide a wide range of salinity habitats that are needed for many animals as they develop through their young stages. The estuaries also provide lots of soft-bottom habitat space for bottom dwellers. Because of the range of salinity habitats available, estuaries are good and important nursery areas; but because estuaries have lower salinity zones, they can also function as refuge areas for small and young animals because many predators (especially larger fish) cannot deal with the lower salinities. Salt marshes are a major feature of Georgia's estuaries.
Salt Marshes: Coastal Georgia is known for its extensive salt marshes. The salt marshes are very productive in terms of plant production that eventually enters the marine food chains. The marshes also provide habitat and protection for young stages of many marine animals; and the marshes function as important nursery areas.
Rock Jetties: Man-made rock jetties along the shore provide stable hard substrata for seaweeds and animals that require hard surfaces for attachment and growth. These rocks allow develop of rocky intertidal communities and shallow rocky subtidal assemblages of animals. Often, along the base of the rock jetties, tide pools form and provide additional habitats for attached invertebrates, mobile invertebrates (such as hermit crabs), and refuges for young fish.
Wide Sandy Shorelines: The wide sandy intertidal shoreline provides a vast area for diggers, burrowers, and tube-dwelling animals. Often the abundance of these animals is not noticed because they live below the sand surface.
Offshore Reefs and Hard Bottoms Nearby: Offshore reefs and hard bottom areas support diverse assemblages of invertebrates including sponges, soft corals, crabs and mollusks. When these off-shore animals get torn off the bottom, they often get carried toward the coast and wash up on our wide, gradually-sloped sandy beaches. These specimens are often surprising treasures for beachcombers.
So, Why is Tybee beach ecology so interesting
Overlap of cold-water and tropical species
Additional species with seasonal changes
Nearby rivers, estuaries, and marshes
Nearby offshore reefs and hard bottoms
Lots of sandy intertidal area
Jetties and tide pools
"You never know what you might find on Tybee's beach!!"