NOTE: This report is available as a PDF file from this site and information will likely be made available from CHNEP on DVD. Information on how to place an order will be posted on this site.

Executive Summary

Since the time of discovery by Ponce de Leon in 1513, Europeans learned what the Native Americans had known for centuries that Charlotte Harbor was biologically diverse with abundant fisheries resources. Despite significant coastal development the condition of the bay remained good enough that in 1995, Governor Lawton Chiles nominated Charlotte Harbor as an “estuary of national significance.” As a result of this nomination, Charlotte Harbor was accepted into the National Estuary Program, one of only 27 other watersheds in the United States.

The Charlotte Harbor National Estuary Program (NEP) encompasses a watershed area of 4,400 square miles and includes all or part of 8 counties. The productivity of the Harbor is a result of the abundant and diverse wetland habitats, such as mangroves and marshes, expansive shallows which harbor numerous seagrasses and intertidal flats and the freshwater nutrient inputs of three river systems. A common and critical biological element that spans all wetland habitats is the benthic invertebrate fauna that inhabit the soils of these habitats.

This project consisted of a Harbor-wide dry season synoptic survey of the benthic fauna inhabiting the principal estuarine habitats within the NEP boundaries. It is the first synoptic sampling of the benthos of multiple habitats in this region. The benthic macrofaunal community consists as a subtly changing gradient of species across the extent of the benthos. Benthic fauna are present everywhere there is water, unless there is something terribly wrong with the quality of the water or the sediment.

Benthic communities are comprised of a multitude of plants and animals including; seagrasses, algae, fishes, worms, shrimp, crabs, mollusks, and many other organisms. The majority of the fauna of benthic communities consist of a group collectively referred to as invertebrates. Invertebrates are defined as animals without backbones, or animals that are not vertebrates. Collectively they represent the majority of animal life on earth, although they represent many different animal phyla. They play a fundamental role in the transfer of energy through the food chain and are the mechanism of recycling the organic debris that settles to the bottom of any water body.

Within the Charlotte Harbor NEP defined system there are 10 basins or zones that are delineated based on bay boundary topography. The 10 areas consist of;

• Coastal Venice, including Lyons, Dona and Roberts Bays;

• Lemon Bay and tidal tributaries;

• Charlotte Harbor “proper”;

• Tidal Myakka River;

• Tidal Peace River

• Tidal Caloosahatchee River;

• Pine Island Sound;

• Matlacha Pass;

• San Carlos Bay and

• Estero Bay and tidal tributaries.

The principal natural benthic habitats within each of the ten drainage basins were sampled for this project and consisted of:

• Mangroves,

• Intertidal sand bar – often exposed at low tide,

• Submerged (subtidal) sand bar – rarely or never exposed at low tide,

• Intertidal mud flats – often exposed at low tide,

• Submerged (subtidal) mud flats – rarely or never exposed at low tide,

• Saltwater marsh,

• Oyster and

• Submerged aquatic vegetation habitats, (SAV) seagrass in this survey

From this sampling effort a total of 65 basin-habitat combinations were sampled across the Charlotte Harbor study area with a total of 195 core samples and 195 sweep net samples. The analysis of these samples resulted in distinguishing 370 invertebrate taxa from more than 44,000 organisms. The results provided a good random representation of the organisms comprising the benthic community for these habitats. This may seem like a large number of species and organisms, however, the benthic community is dynamic and a long term intensive sampling program would likely increase the species list to several thousand species.

Of the 370 taxonomic designations eight accounted for slightly more than 50% of the 44,000 organisms that were collected and 90% of the fauna were represented by only 61 taxa (16% of the total taxa). The top 5 most numerically abundant species from each habitat and basin accounted for slightly more than 79% of the total individuals collected. These species are the dominant organisms of the benthos in the NEP study area.

Species dominance is not uncommon in benthic habitats although the composition of the dominant species also changes spatially and on a temporal basis. The dynamic range of he composition of benthic communities is likely a critical component of ecosystem stability analagous to the role of insects in terrestrial ecosystems.

The number of species collected from a site ranged from 7 at the Estero Bay marsh habitat to 79 at the San Carlos Bay subtidal sand site. The average number of species recovered from a site was 28 and the median was 24 species.

Salinity plays a clear role on the species richness of an area. Basins that exhibited the highest salinity values included Coastal Venice, Lemon Bay, Pine Island Sound, San Carlos Bay and Estero Bay, and these basins exhibited the greatest overall numbers of species. The basins with the lowest salinity, Myakka, Peace and Caloosahatchee Rivers illustrated the fewest number of taxa.

The greatest number of species was collected from the subtidal mud and sand habitats, which averaged 39 and 38 species respectively, followed by SAV habitat, oyster habitat, mangroves, intertidal mud, intertidal sand and salt marsh. For 5 of the eight basins intertidal mud exhibited a greater number of species than intertidal sand. For two basins the intertidal sand had a greater species count and for Matlacha Pass no suitable intertidal mud habitat could be located. For the eight basins there was an even split for the habitat, mud versus sand, exhibiting the most species.

For habitats with vegetation, and oysters the number of taxa collected ranged from 7 to 59 taxa. Seagrass habitat exhibited the greatest number of species followed by oyster habitat, mangroves and salt marsh. The salt marshes in this region are often seasonally and tidally "dry" resulting in a depauperate benthic fauna.

The most diverse basin was Lemon Bay which from which 160 invertebrate taxa were recovered from all habitats combined. The most productive basin in terms of organism abundance was San Carlos Bay which exhibited an overall abundance of 130,000 organisms/m2, compared to a range of16,623 to 72,292 organisms/m2 for all of the other basins.

The number of individuals collected from a sample within a habitat ranged from 9 to 8,365 specimens (Estero Bay marsh and San Carlos Bay subtidal sand) with a mean of 578 individuals per sample and a median of 288 individuals per sample. Converted to numbers per square meter the number of organisms ranged from 722 to 670,918 with a median value of 23,059/m.

The number of species and their abundance illustrates the tremendous variance in numbers of organisms that is commonly exhibited within benthic habitats. The benthos is a very productive habitat. From a human perspective consider a person that is wading into the subtidal zone will have on average about 588 benthic organisms under each foot.

Representative sediment samples from each site were analyzed and illustrated that the basic soil component consists of fine to coarse quartz sand with widely varying subcomponents of shell fragments, silt, clay and organic material. The mix of these elements is determined by physical forces and in some cases the modifing influences of the biological components such as oysters, mangroves, marshes, and submerged aquatic vegetation.

The results of the project illustrate that in general the upper estuary, lower salinity regions; exhibit the greatest abundance of organisms, but have a lower overall species diversity. This relationship is a paradigm of estuarine ecology. Freshwater brings nutrients and organic matter into the sea via the mixing zone known as the estuary. Within the estuary the high nutrient levels allow for abundant primary production. The invertebrates that are adapted to the lower and fluctuating salinities of the estuary can exploit the primary production and may become extremely abundant. However, only a small portion of the diversity of species within the oceans can tolerate the conditions of the estuary and therefore the diversity of invertebrates within the upper estuary is lower than that of the more saline waters of the lower estuary.

The relevance of the benthos to humans is that these organisms are the principal agents of energy transfer from primary production to fisheries. Because the benthos is very diverse it offers a plasticity of response to changing conditions in the estuary. Fishes feed on a multitude of benthic inhabitants perhaps most notably on the microcrustaceans. The crustaceans are able to exploit the phytoplankton and benthic algae and diatoms which enable rapid growth and reproduction. They also frequently swarm off the bottom at night to be carried by tides where they settle on the most favorable habitat as controlled by salinity and substrate. Juvenile fishes in turn follow the food and seek out shelter in the seagrass, mangroves and marsh edges.

Benthic communities are sensitive to changes in the conditions of the water quality or sediment. For this reason the benthos is often use as an environmental indicator for determination of the impacts of pollutants, hydrologic alterations and sediment disturbance. Only in very severely polluted or otherwise disturbed areas are benthic communities absent.

The body of this report provides a great deal of information describing relevance of the Charlotte Harbor Benthic habitats and the composition of the fauna. This project was conducted during the dry season and species composition will be considerably different in some areas during the wet season. However, the fundamental forces that determine diversity and abundance remain the same.

The results of this project are contained on a single compact disk (CD). The report document is presented as an Adobe PDF file titled Charlotte Harbor Benthic Biodiversity Report and is approximately 14 megabytes in size. A supplement to the report which illustrates some of the common benthic macroinfauna is also presented in PDF and is titled Common Macrobenthic Invertebrates of Charlotte Harbor (~42 mb). Both of these documents have hyperlinks to internet sources of additional information.

In addition to the report there are four file folders contained on the CD labeled, Data, Images, Maps and SHP files.

Data folder: Contains the raw data from this study as well as species lists from additional benthic studies conducted in the Myakka and Peace Rivers and invertebrate data for Mullock and Hendry Creeks that were provided by Ford Walton of the Florida Department of Environmental Protection. Data are formatted in a Microsoft Excel workbook and in Access. Slightly more information is contained in the Excel file as well as graphics.

Images folder: This file contains 12 folders of images including aerial images, some sample photographs of invertebrates, and pictures of habitats and field sampling efforts.

Maps folder: This folder contains individual images of maps, most of which were presented in the report.

SHP folder: This folder contains Geographic Information System (GIS) files necessary to reconstruct most of the mapping products presented in the report.

Within the database files there are several tables with a field labeled as NODC. The NODC Code is a phylogenetic numbering system developed by the National

Oceanographic Data Center (NODC).http://www.nodc.noaa.gov. A detailed explanation of the code can be found at http://www.nodc.noaa.gov/General/CDR-detdesc/taxonomicv8.html. In 1996, NODC released the final version (#8) of the NODC Taxonomic Code on CD-ROM. This CD-ROM, now out of date, provided the old NODC codes along with their new ITIS Taxonomic Serial Numbers to facilitate the transition to a new Integrated Taxonomic Information System (ITIS). From that point in time the NODC code was frozen, and ITIS assumed responsibility for assigning new TSN codes, and verifying accepted scientific names and synonyms. We have found the code to remain versatile for certain computer applications related to the sorting and analysis of species abundance data.

Any use of information of images presented in this document should be cited appropriately.