General Patterns of Island Biotic Dynamics

• Island ponds are characterized by relative isolation & unique settings

• Islands may have inherent limitations on size and spatial diversity

• May be characterized by an absence of certain resources

• Island species may be significantly differentiated from mainland species

• Lowered biotic diversity may include reduced invertebrate predator pressure

• Biotic communities may reflect the unique character of an island

• Protozoan communities may therefore be characterized by unique biotic associations

• These island studies are designed to explore microbial community dynamics

Role of Protozoa in Aquatic Food Chains

• Bacteria and protozoa may account for 50% of benthic respiration

• Protozoa show diverse patterns of interspecies interactions

• May develop "symbiotic population control complexes"

• Elaborated predator/prey relationships may be altered on islands

Effects of Land Use on Island Ponds

• Greater human activity may result in increased contact with mainland species

• Increased development may bring pollution and/or change evolutionary dynamics

• Island ponds on developed islands may more closely resemble mainland ponds

Is There an "Island" Effect?

• Located about 9 miles offshore, in Block Island Sound

• Observations on 9 Freshwater or Brackish Ponds (1976-1985)

• Samples taken from shallow sediments (top 1 cm. sediment)

• Phase Contrast Microscopy (live observations)

General Patterns

• Predators seem to control protozoan populations

• Microbial communities are similar to those found in similar mainland ponds

• Metazoan predators exceed protozoan predators in benthic communities

• Species diversity appears to be directly related to pond volume

• No noticeable "island" effect has been found

Ecology of Rhode Island's Islands: Focus on Block Island

Rhode Island Natural History Society (RINHS) Conference 2000

Photos of Block Island Ponds

• Located in Buzzards Bay in Massachusetts (near Cuttyhunk Island)

• Small island, exposed to extreme weather conditions

• Observations on 7 Freshwater or Brackish Ponds (1976)

• Samples taken from shallow sediments (top 1 cm. sediment)

• Phase Contrast Microscopy (live observations)

General Patterns

• Predators seem to control protozoan populations

• Selective forces may have favored encystment in protozoan species

• Location and weather conditions may have encouraged highly adapted communites

• Great variation among Penikese Island ponds

• Microbial communities appear to be somewhat different from mainland ponds

• (more studies needed to make comparisons)

• Metazoan predators may have replaced protozoan predators in some ponds

• Species diversity among protozoa appears to be related to pond volume

• Island located in Narragansett Bay

• Linked to other studies within an estuarine sanctuary

• (South end of island is protected from further development)

• Observations on 2 Freshwater or Brackish Ponds (1999-Present)

• Samples taken from shallow sediments (top 1 cm. sediment)

• Phase Contrast Microscopy (live observations)

General Patterns

• Microbial communities are similar to those found in similar mainland ponds

• Studies are ongoing, data will be compared with other island pond studies

Photos of Prudence Island Ponds

Conclusions About Distribution of Island Protozoa

• Island ponds provide unusual opportunities to examine the evolution of trophic dynamics among aquatic microbiota

• Differentiation from mainland ponds is a function of several factors:

  • Distance offshore

  • Weather patterns

  • Degree of human development

  • Natural selection within microbiotic communities

General Parameters to Assess in Making Comparisons

• Predation patterns within microbial community

• Genetic variation among protozoa

• Size and complexity of food chains

• Role of micrometazoans in controlling protozoan populations

Narragansett Bay Estuary Sanctuary

(Site of bioremediation cleanup at a former U.S. Navy Fuel Depot)

Site Description & Analysis

• Island located in Narragansett Bay - near mainland

• South end of island protected from further development

• Observations on 2 sandy beaches near bioremediation area (1999-Present)

• Samples taken from shallow sediments (top 1 cm. sediment)

• Physical parameters recorded (temperature, salinity, dissolved oxygen)

• Hydrocarbon analysis conducted 2000-2001

• Phase Contrast Microscopy (live observations)

• Assessment of protist populations

• Photomicrography & scanning techniques utilized

Hypotheses

• Petroleum HCNs will be similar to compounds found in the bioremediation area

• Volatile organic compounds will be high as a result of biosparging technique

• Oiled communities will resemble those found in earlier mesocosm studies

General Findings

• Oil/gasoline residues are visible in the intertidal zone

Photos of Contaminated Beach

• Petroleum HCNs found in intertidal zone are similar to nearby

• monitoring wells in bioremediation area

• VOCs are present in intertidal samples (BTEX profile),

• indicating presence of residues of gasoline

Table I: Petroleum Hydrocarbons Found at Prudence Island Bioremediation Site

• Microbial communities are similar to those found in other oil contaminated sites

• (emergence of large, diatom-eating ciliates; reduced numbers in selected microinvertebrate populations; high numbers of diatoms)

Figure 1: Microbial Populations in Control & Oiled Intertidal Marine Microbial Communities

• Oiled microbial communities are comprised of different species and show

• altered community structure and trophic dynamics

Table II. Differential Species Composition in Control & Oiled Habitats

• Studies are ongoing; database will remain accessible via this Web Site (including previous field and mesocosm studies)

Database (Microbial Species Found in Oiled Communities)