# Jeremy Johnson Russ Frydenborg Florida Department of Environmental Protection Division of Environmental Assessment and Restoration

# Loxahatchee Estuary

# The Loxahatchee Estuary 

# Geographical and Physical Description

 The Loxahatchee estuary includes the marine, polyhaline and meso / oligohaline portions of the Loxahatchee River between the river and where it meets the Atlantic at Jupiter Inlet

 

### The watershed for the estuary includes areas in northeastern Palm Beach County and southeastern Martin County, and major cities and towns in the watershed include Jupiter, Tequesta, Juno Beach, Jupiter Island, Jupiter Inlet Colony, Jupiter Farms, Hobe Sound, and Palm Beach Gardens

 

### The Loxahatchee River is classified as Class II (shellfish harvesting) and has been designated as an Outstanding Florida Water (OFW).

### Physical Characteristic Values Source
Estuarine surface area (km 2) 988 acres Loxahatchee River Environmental Control District Mean depth (m) 1 - 3 ft. Loxahatchee River Environmental Control District Temperature 14° C- 32° C Loxahatchee River Environmental Control District Salinity Range: 0- 33 PSU Loxahatchee River Environmental Control District
Residence Time < 1 day Mixed Semi- Diurnal Tide 60% of Freshwater is flushed at each tide Loxahatchee River Environmental Control District

# Loxahatchee Estuary Land Use

Acres Percent Description 31077 21.10% Urban 17605 11.95% Ag 5786 3.93% Shrub/Brushland 26614 18.07% Forested 11345 7.70% Open Water 51315 34.84% Wetland 743 0.50% Beaches/Disturbed 2796 1.90% UtilitiesResponse

variable Observed historically? Observed currently? Explanation Source

Low DO (hypoxia/anoxia) No No Currently, DO is considered to be high in the estuary and is meeting the Class III requirements. Loxahatchee River Environmental Control District

Reduced clarity No No None have been reported but continued monitoring is warranted. Loxahatchee River Environmental Control District

Increased chlorophyll a concentrations No Yes A slight increase in the “polyhaline” portion of the Loxahatchee has been reported, which can be attributed to the hydrological modification. Loxahatchee River Environmental Control District

Phytoplankton blooms (nuisance or toxic) No No No phytoplankton blooms have been reported for the system.Response

variable Observed historically? Observed currently? Explanation Source

Problematic epiphyte growth No No No problematic epiphyte growth has been reported for the system. Problematic macroalgal growth No No No problematic macroalgal growth has been reported for the system. SAV community changes or loss No No SAV continues to increase in the area and is not cause for concern. Loxahatchee River Environmental Control District

Emergent vegetation community changes or loss Yes Yes The altered salinity of the Loxahatchee Estuary has allowed estuarine plants to out compete fresh water trees that once lined the river banks. As the saltwater intruded the soils, many trees were Loxahatchee River Environmental Control District**Response Variable**  **Observed Historically?**  **Observed Currently?**  **Explanation Source** 
Coral/ Hardbottom community changes or loss N/A N/A N/A

Impacts to Benthic Community No No None reported, although not well studied

Fish Kills No No No fish kills have been reported in the systemFactors Observed? Explanation Source

Increased nutrient loading or concentrations from historical levels No None that have been observed. Loxahatchee River Environmental Control District Mitigating factors that could prevent nutrient expression No None that have been observed. Loxahatchee River Environmental Control District Other significant stressors to biological communities Yes Salinity Issues attributed to flow reductions and the dredged inlet. Loxahatchee River Environmental Control District Natural episodic events contributing to nutrient regime (e.g., seasonal or hydrologically driven) Yes Hurricanes and other storms have impacts. Loxahatchee River Environmental Control District

# The Loxahatchee Estuary 

# Biological Summary

 

## Seagrass Communities
 

## Seagrass beds in the estuary are dominated by Johnson’s Seagrass Halophila johnsonii, Shoal Grass Halodule wrightii, Paddle Grass Halophila decipiens, and Manatee Grass Syringodium filiforme 

##  

# The increase in the distribution of SAV in the Loxahatchee from 1998 to 2007 has been extraordinary.  

# This increase has been attributed to the ongoing hyrdologic restoration efforts in the Loxahatchee basin.

# The Loxahatchee Estuary 

# Biological Summary

1998 SAV coverage in the Loxahatchee estuary. 

# 2007 SAV Coverage

# The Loxahatchee Estuary 

# Biological Summary cont.

 

## Oysters
 

## Two species of oyster were observed in the estuary of the Loxahatchee River, the American or Eastern Oyster, Crassostrea virginica, and the Flat Oyster, Isognomon alatus

 

## The data collected from the sampling points indicate that the greatest number of beds, the largest spatial distribution, and the highest densities were recorded in the Northwest Fork.

# The Loxahatchee Estuary Biological Summary

 

### The Loxahatchee Estuary is fully meeting its designated uses of “Recreation, Propagation and Maintenance of a Healthy, Well

- balanced Population of Fish and Wildlife” based on the following information:

 

### The most sensitive biological endpoint in the Loxahatchee Estuary is seagrass, and the seagrass habitat is healthy and actually expanding in coverage.

 

### The seagrass beds are large, diverse and continuing to grow after the destructive 2004 Hurricane season

 

### Fish and invertebrate data show high abundances in seagrass beds

# The Loxahatchee Estuary 

# Sources of Nutrients

 

# Loxahatchee River
 

# Wetlands/leaf litter

 

# Stormwater Runoff

 

# Atmospheric Deposition

# Water Quality Studies Mean Annual TN

TN in the Loxahatchee from 1998 to 2009.

# Water Quality Studies Mean Annual TP

TP in the Loxahatchee from 1998 to 2009.

# Water Quality Studies Mean Chl

- a

Chl-a in the Loxahatchee from 1998 to 2009.

# Proposed numeric nutrient criteria for Total Nitrogen in the Loxahatchee Estuary (mg/L) Proposed Criteria Marine Polyhaline Meso/Oligohaline Existing Long Term

Geometric Mean 0.62 0.97 1.16 Maximum Allowed Long Term Geometric Mean 0.68 1.07 1.28 Annual Geometric Mean for the Network of Stations (2 of 5 year exceedance rate) 1.11 1.48 1.54 Annual Geometric Mean for a Single Site (2 of 5 year exceedance rate) 1.19 1.56 1.59

# Proposed numeric nutrient criteria for Total Phosphorous in the Loxahatchee Estuary (mg/L) Proposed Criteria Marine Polyhaline Meso/Oligohaline Existing Long Term

Geometric Mean 0.019 0.039 0.067 Maximum Allowed Long Term Geometric Mean 0.021 0.043 0.074 Annual Geometric Mean for the Network of Stations (2 of 5 year exceedance rate) 0.027 0.052 0.09 Annual Geometric Mean for a Single Site (2 of 5 year exceedance rate) 0.03 0.059 0.107

# Proposed numeric nutrient criteria for Chl-a in the Loxahatchee Estuary ( ug /L) Proposed Criteria Marine Polyhaline Meso/Oligohaline Existing Long Term

Geometric Mean 2.9 7.9 5.1 Maximum Allowed Long Term Geometric Mean 3.2 8.7 5.6 Annual Geometric Mean for the Network of Stations (2 of 5 year exceedance rate) 4.2 11.4 7.0 Annual Geometric Mean for a Single Site (2 of 5 year exceedance rate) 5.1 13.0 7.5

# The Loxahatchee Estuary 

# What’s next?

• 

# Provide additional comments on estuary report to Jeremy Johnson

• 

# Phone: 850

- 245 - 8129

• 

# Email: Jeremy.K.Johnson@dep.state.fl.us

• 

# Finalize estuary reports.