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Coastal River Systems - University of Florida Studies

The first comprehensive sampling of the Coastal rivers of Citrus County was carried out by Frazer et al. (2001a). The general objective of this original work was to describe quantitatively the physical, chemical and vegetative characteristics of each of selected rivers along Florida's Springs Coast. The impetus for the investigation was a concern for elevated nitrate concentrations in groundwater that enter each of the rivers as spring discharge.

Nitrate is a nutrient that occurs naturally in aquatic systems, including these spring-fed coastal rivers. It is assimilated by aquatic plants and algae and is one of many nutrients that contribute to their growth. An increase in the supply of nitrate (or other limiting nutrient such as phosphorous), however, has the potential to over-stimulate plant and algal growth with negative ecological consequences. In fact, excessive nutrient enrichment may favor the development of nuisance plant and algal species and ultimately lead to the decline of native vegetation. Increased periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. growth on rooted aquatic plants as a consequence of increased nutrient input can exacerbate the situation. Such a scenario is a commonly observed eutrophication progression scheme in aquatic systems worldwide. The potential eutrophication of the rivers, as a result of increased nitrate delivery, remains a primary concern for water resource managers.

Nitrate concentrations have increased significantly in the river systems. The mean nitrate concentration at the uppermost sampling transect in the Weeki Wachee River, for example, between 1998 and 2000 was 524 µg L-1. Between 2003 and 2005, the mean nitrate concentration at this same transect was 781 µg L-1. This more recent value represents an approximate 50% increase in nitrate concentration relative to the earlier time period. Similar comparisons indicate a 20% increase in the mean nitrate concentration at the uppermost sampling transect in the Chassahowitzka River and a 6% increase in the Homosassa River. The increases in nitrate concentration coupled with concomitant increases in flow rates in each of the three rivers has resulted in substantially greater nitrate loads.

In fact, calculated nitrate loading rates in the headwater regions of the Weeki Wachee, Chassahowitzka and Homosassa rivers have increased by 76%, 43% and 56%, respectively, since the 1998 to 2000 sampling period.
Soluble reactive phosporus concentrations have also increased significantly in each of the river systems. This is particular reason for concern given that previous work in these rivers has indicated a strong potential for phosphorus limitation of algal growth. In the upper regions of the Weeki Wachee River, for example, mean soluble reactive phosphorus concentrations increased by as much as 21% since the 1998 to 2000 sampling period. Increases of 19% and 15% were documented in the upper regions of the Chassahowitzka and Homosassa rivers, respectively. Loading rates calculated at the uppermost sampling transects in the Weeki Wachee, Chassahowitzka and Homosassa rivers increased by 33%, 44% and 46%, respectively, between the 1998 to 2000 and 2003 to 2005 sampling periods.

Coincident with the increased nitrogen and phosphorus concentrations and higher nutrient loading rates, were marked declines in submersed aquatic vegetation (SAV) in each of the three rivers. The Weeki Wachee River exhibited an approximate 75% reduction in mean SAV biomass. A similar reduction was observed in the Homosassa River, i.e. 67%. An approximate 31% reduction in mean SAV biomass was observed in the Chassahowitzka River. Noteworthy is the decline in the frequency of occurrence of native species such as Vallisneria americana in the Homosassa River and Sagittaria kurziana in the Chassahowitzka River. The abundance of periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. associated with rooted macrophytes increased significantly in both the Homosassa and Chassahowitzka. In fact, mean periphyton abundance on the remnant macrophyte population in the Homosassa was nearly twice as high (85% increase) during the 2003-2005 sampling period than in the 1998-2000 sampling period. In the Chassahowitzka River, the increase in mean periphyton abundance on macrophytes was 30%.

The changes noted above are, in combination, legitimate reasons for concern. Increased nutrient delivery, loss of native macrophytes and increased periphyton loads are symptomatic of eutrophication related phenomena. The potential broader consequences of nutrient over-enrichment on the ecological health and integrity of the Weeki Wachee, Chassahowitzka and Homosassa rivers, however, has yet to be fully investigated. Continued monitoring of these systems is essential to evaluate the effectiveness of ongoing nutrient reduction strategies and future remediation efforts aimed at reversing the negative effects of nutrient over-enrichment.

INTRODUCTION (The following is taken from reports of the Univerity of Florida submitted to the Southwest Florida Water Management District in August, 2006, under Conract Numbers, 03CON000038 and 04CON000081).

In August, 2006, teams from the University of Florida led by Thomas K. Frazer submitted reports to the Southwest Florida Water Management District on water quality and vegetative evaluations concerning the coastal rivers of Citrus County, the Weeki Watchee River of Hernando County and adjacent Gulf Coast waters. The following narative, together with extracts included under the particular rivers,is based upon those reports.

Ground water nutrient enrichment presents a potentially serious ecological issue for much of central Florida. Because of the occurrence of the large aquifer systems and highly permeable karst geology, there are numerous locations and multiple pathways by which nutrient-enriched ground water can permeate and mix with the surface waters. Freshwater springs, for example, provide a direct conduit for nutrient-enriched ground water to move from the aquifer to surface waters. As nutrient-laden ground water enters the surface water system, largely via the springs, there is the potential for adverse ecological changes to occur downstream. Increases in stream nutrient concentrations/loads, for example, have been linked to changes in autotrophic community composition, vegetative biomass, and an increase in nuisance species (Wong and Clark 1976; Mace et al. 1984; Wright and McDonnell 1986a, 1986b). Such changes can, in turn, affect shifts in community structure and alter food web dynamics (see Hershey et al. 1988; Peterson et al. 1993). In extreme cases, the ecological health and integrity of a system may be severely compromised as a consequence of increased nutrient inputs.

Concerns over the potential effects of increased nutrient delivery to the rivers was raised nearly a decade ago when Jones et al. (1997) reported elevated nitrate concentrations within ground water emanating from the springs and/or complexes of springs that feed each of those systems. At that time, however, there were few quantitative data available that would allow scientists or water resource managers to determine whether or not the ecological character of these specific river systems had been or might be affected by an increase in nitrate. Frazer et al. (2001a) subsequently provided the first quantitative assessment of the Homosassa, Chassahowitzka, and Weeki Wachee rivers. As part of that assessment, the investigators determined that light availability and salinity were major factors affecting the abundance and distributional patterns of submersed aquatic vegetation (see also Hoyer et al. 2004). However, they also reported significant statistical relationships between nitrate and soluble reactive phosphorus and submersed aquatic vegetation and periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. growth on macrophytes in both the Homosassa and Chassahowitzka rivers and indicated that additional nutrient inputs to these rivers could lead to changes in the vegetative community.

The conclusion to the report on the Homosassa, Chassahowitzka and Weeki Watchee rivers asserted that similar results were likely for the Crystal River/ Kings Bay and lower Withlacoochee river.

In the three rivers study, more recent data is compared with data generated as part of the earlier assessment of these systems to deduce the changes that occurred over the entire period. The comparisons are quantitative in nature and statistically rigorous. The findings are compelling and merit the immediate and close attention of water resource managers whose aims are to prevent further water quality degradation and to protect the ecological integrity of these natural spring-fed systems.

Scope of Project

Sampling for the project was carried out in the Homosassa, Chassahowitzka and Weeki Wachee rivers between 2003 and 2005. The materials and methodologies employed were identical to those used in an earlier investigation of these same systems between 1998 and 2000. The focus of this report is accordingly on a comparison of the two temporally distinct, but otherwise identical, data sets.

The primary questions to be addressed (see below) relate primarily to the issue of nutrient enrichment and the potential effects on submersed aquatic vegetation in the aforementioned rivers. Although concern over increases in nitrate concentrations were a major driving force behind the original assessment of these spring-fed systems, a recent recognition that increased phosphorus delivery is likely to adversely influence the ecology of the Homosassa, Chassahowitzka and Weeki Wachee rivers has prompted the more general use of the phrase "nutrient enrichment".

(1) Have nutrient concentrations, nitrate and soluble reactive phosphrous in particular, increased in each of the three spring-fed rivers?

(2) If so, have there been concomitant changes in the abundance of submersed aquatic vegetation?

(3) Has there been an increase in the periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. associated with host macrophytes?

Answers to these questions are intended to inform water resource managers of potential changes in the nutrient composition of the rivers and issues that may result from these changes. They will serve as justification for the development and implementation of nutrient reduction strategies and other conservation related activities. The answers, however, are not sufficient to evaluate the effectiveness of those strategies and/or particular management actions. A long-term and sustainable monitoring program is essential for that purpose.

Land use within the Springs Coast region has a rural character despite intensive growth in the last 30 years. This is largely due to extensive and relatively undeveloped coastal marshes, inland swamps, as well as forested properties under the ownership and/or management of both private individuals and government agencies. Development, however, is increasing rapidly in some areas, particularly in the Spring Hill area near the Weeki Wachee River and also in the Crystal River/Homosassa Springs areas (SWFWMD 2001). Continued population growth in the region, fueled by the development of the Springs Coast Parkway, is expected to continue (SWFWMD 2001).

Submersed Aquatic Vegetation
Frequency of Occurrence and Patterns of Distribution

A comparison of data from the 1998-2000 and 2003-2005 project periods indicated notable declines in the frequency of occurrence of submersed aquatic vegetation in all three of the rivers investigated. In the Weeki Wachee River, there was a 56% increase between 1998-2000 and 2003-2005 in the mean number of sampling stations devoid of submersed aquatic vegetation. In the Chassahowitzka and Homosassa rivers, the mean number of sampling stations without plants or macroalgae increased by 80% and 104%, respectively. Loss of submersed vegetation was most evident at downstream locations in the Chassahowitzka and Homosassa rivers. Although Hoyer et al. (2004) indicated that salinity was a primary factor affecting the distributional patterns and downstream occurrence of plants and algae in both of these systems, it should be noted that mean salinities in all three systems were significantly less in 2003-2005 than in 1998-2000. This leads us to suggest that factors other than an increase in salinity underlie the observed declines in the frequency of occurrence and general downstream decline of submersed aquatic vegetation.

Changes in the frequency of occurrence of particular taxa within each of the three rivers are indicated. Highlighted below are the key findings as they relate to changes in native macrophytes as well as plants and algae that are considered to be nuisance species.

In the Weeki Wachee River, Sagittaria kurziana and Vallisneria americana (both native angiosperms) exhibited declines in their frequencies of occurrence. The percent change as indicated by presence/absence at all sampling stations visited during the two project periods was -45% and -11%, respectively. An inspection of graphical data shows that Sagittaria kurziana has retreated upstream with this species occurring only at the uppermost transects during the most recent sampling period, i.e. 2003-2005. Vallisneria americana, which occured only in the lower portions of the river, exhibited no clear pattern associated with the decline. Najas guadalupensis, another native macrophyte, exhibited a 56% increase in frequency of occurrence between 1998-2000 and 2003-2005, due largely to its' increased presence in the middle and lower portions of the river. There is some indication, however, that this species has exhibited a downstream retreat. Hydrilla verticillata, a non-native and invasive species, exhibited a 32% decline in frequency of occurrence between 1998-2000 and 2003-2005. Interestingly, this species only occurred in downstream of Transect 4 during both project periods. The reported decline reflects a generally thinning ofHydrilla verticillata. Filamentous macroalgae, as a composite group, declined by 12%. This change that can be attributed largely to reduced frequencies in the lowest portions of the river. The native alga, Chara sp., exhibited a marked increase in frequency of occurrence between 1998-2000 and 2003-2005. Chara sp. was present at only one sampling station and only during one sampling event during the initial project period, i.e. 1998-2000. In 2005, however, Chara sp. was present in 14% of all sample collections. Ruppia maritima, which was not present in the Weeki Wachee River between 1998-2000 was observed at one sampling station in 2005. We also noted the presence of the marine macroalga, Caloglossa sp., at a single station in 2005, but have not included it in our presentation of the data as the focus is on freshwater species.

In the Chassahowitzka River, notable declines in the frequency of occurrence of Ceratophyllum demersum, Sagittaria kurziana and filamentous algae were documented between 1998-2000 and 2003-2005. The percent change of Sagittaria kurziana as indicated by presence/absence at all sampling stations visited during the two project periods was -80%, and no specimens were observed at any sampling station after 2003. Filamentous algae decreased in frequency of occurrence by 42%, with the majority of the loss occurring in the lower portion of the river. Ceratophyllum demersum, which was present in the river every year between 1998 and 2000, was not observed at any sampling location between 2003 and 2005. Conversely, Chara sp. and Potamogeton pusillus were not observed in the river between 1998 and 2000, but were present during the more recent sampling period. Gracilaria sp., considered primarily a marine alga, exhibited a 56% increase in frequency of occurrence between 1998-2000 and 2003-2005). Much smaller increases in the frequency of occurrence were exhibited by Potamogeton pectinatus (9%), Najas guadalupensis (8%), Myriophyllum spicatum (8%), Vallisneria americana (2%) and Hydrilla verticillata (1%).

In the Homosassa River, there was a marked reduction in the frequency of occurrence of filamentous algae between 1998-2000 and 2003-2005 (53%). Macrophytes, however, often exhibited similar or even greater declines in their frequencies of occurrence. For example, the native macrophyte, Vallisneria americana, which occurred at 6% of sampling stations between 1998 and 2000, was observed at only 2% of sampling stations between 2003 and 2005. This equates to a 67% decline. Ceratophyllum demersum andNajas guadalupensis, two other native macrophytes, exhibited declines in frequency of occurrence of 65% and 40%, respectively. The native alga,Chara sp., although observed in 1999 had no record of occurrence during the 2003-2005 project period. Hydrilla verticillata and Myriophyllum spicatum, both non-native species, exhibited declines of 33% and 67%, respectively, in their frequencies of occurrence. Only Potamogeton pusillus and the brackish grass, Ruppia maritima, exhibited increases in frequency of occurrence; 47% and 40%, respectively.

Macroalgal Biomass

Significant declines in macroalgal biomass in each of the three rivers were evident, though the percentage change was less than that reported for macrophytes in both the Weeki Wachee and Homosassa rivers. Only the Chassahowitzka River exhibited a greater relative decline in macroalgae.

In the Weeki Wachee River, the mean macroalgal biomass for 1998-2000 was 0.91 kg wet wt m-2. Between 2003 and 2005, the mean macroalgal biomass value (0.39 kg wet wt m-2) was significantly less (ANOVA, df = 19, F = 25.38, P < 0.0001). This represents an approximate 57% reduction in macroalgal biomass between the two project periods. As previously indicated, this difference between the projects was due largely to a reduction in the biomass of filamentous macroalgae in the upper and middle portions of the river.

In the Chassahowitzka River, the mean above-ground macroalgal biomass decreased between project periods by approximately 73%. During the 1998-2000 project period, the mean macroalgal biomass was 0.49 kg wet wt m-2, while during the 2003-2005 project period, the mean above-ground macroalgal biomass was 0.13 kg wet wt m-2. This difference was statistically significant (ANOVA, df = 19, F = 40.57, P < 0.0001) and represents a general reduction in macroalgae throughout the river.

In the Homosassa River, the mean macroalgal biomass for 1998-2000 was 0.50 kg wet wt m-2. Between 2003 and 2005, the mean macroalgal biomass value (0.19 kg wet wt m-2) was significantly less (ANOVA, df = 19, F = 25.38, P < 0.0001). This represents a reduction in macroalgal biomass of 62% between the two project periods. The decline in macroalgal biomass was most notable in the middle section of the river. Noteworthy is the fact that macroalgae are more prevalent in the Homosassa River than are macrophytes.

Periphyton Associated with Macrophytes

Based on findings by Notestein et al. (2002), we expected the observed increases in nutrient concentrations and associated nutrient loading rates in each of the three rivers to be manifested as increases in periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. abundance on host macrophytes. Periphyton associated with rooted macrophytes did, in fact, increase significantly between 1998-2000 and 2003-2005 in both the Chassahowitzka and Homosassa rivers (see below). However, in the Weeki Wachee River, periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. abundance decreased significantly (see below) during the same time interval.

In the Weeki Wachee River, the mean periphyton measure for 1998-2000 was 0.078 mg chl/g wet wt host macrophyte. Between 2003 and 2005, the mean periphyton abundance on host macrophytes, 0.035 mg chl/g wet wt host macrophyte, was significantly less (ANOVA, df = 9, F = 24.01, p = 0.008). This represents an approximate 55% reduction in periphyton abundance on macrophytes in this system, which may be due to the decline of Hydrilla verticillata, which can support a substantial accumulation of periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. biomass. It is possible also that increased flow rates between 1998-2000 and 2003-2005 promoted sloughing of periphyton resulting in the lower values throughout the river during the most recent project period.

In the Chassahowitzka River, the mean periphyton measure increased between project periods by approximately 33%. During the 1998-2000 project period, the mean periphyton measure was 0.169 mg chl/g wet wt host macrophyte, while during the 2003-2005 project period, the mean measure was 0.225 mg chl/g wet wt host macrophyte. This difference was statistically significant (ANOVA, df = 9, F = 4.86, P = 0.05) and represents a general increase in periphyton associated with macrophytes throughout the river.

In the Homosassa River, the mean periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. measure increased between project periods by approximately 85%. During the 1998-2000 project period, the mean periphyton measure was 0.089 mg chl/g wet wt host macrophyte, while during the 2003-2005 project period, the mean measure was 0.165 mg chl/g wet wet host macrophyte. This difference was statistically significant (ANOVA, df = 9, F = 27.62, P < 0.001) and represents a general increase in periphyton associated with macrophytes throughout the river.

Concluding Remarks

Increased nutrient delivery to aquatic systems is a global phenomenom and is perhaps the most pervasive problem facing water resource managers today. Increased nutrient loading, particularly of nitrogen and phosphorus, in many instances promotes rapid growth of algae and nuisance vegetation which can, in turn, lead to the decline of native submsersed plants. In extereme cases of nutrient over-enrichment, the biological structure and ecological function of aquatic ecosystems can be severely compromised with long-lasting socioeconomic consequences.

The changes documented in this report for Weeki Wachee, Chassahowitzka and Homosassa rivers between 1998-2000 and 2003-2005 are consistent with a eutrophication progression scheme and warrant the close attention of water resource managers whose charge is to maintain the ecological health and integrity of these systems. Highlighted below are key findings that substantiate this claim.

Nitrate concentrations have increased significantly in all three river systems. Most notable has been the change in the Weeki Wachee River. The mean nitrate concentration at the uppermost sampling transect in the Weeki Wachee River between 1998 and 2000 was 524 µg L-1. Between 2003 and 2005, the mean nitrate concentration at this same transect was 781 µg L-1. This more recent value represents an approximate 50% increase in nitrate concentration relative to the earlier time period. Similar comparisons indicate a 20% increase in the mean nitrate concentration at the uppermost sampling transect in the Chassahowitzka River and a 6% increase in the Homosassa River. The increases in nitrate concentration coupled with concomitant increases in calculated discharge rates in each of the three rivers has resulted in substantially greater nitrate loads. In fact, calculated nitrate loading rates in the headwater regions of the Weeki Wachee, Chassahowitzka and Homosassa rivers have increased by 76%, 43% and 56%, respectively, since the 1998 to 2000 sampling period.

Soluble reactive phosporus concentrations have also increased significantly in each of the three river systems. This is particular reason for concern given that previous work in these rivers has indicated a strong potential for phosphorus limitation of algal growth (Frazer et al. 2001a, Frazer et al. 2002, Notestein et al. 2003). In the upper regions of the Weeki Wachee River, mean soluble reactive phosphorus concentrations increased by as much as 21% since the 1998 to 2000 sampling period. Increases of 19% and 15% were documented in the upper regions of the Chassahowitzka and Homosassa rivers, respectively. Loading rates calculated at the uppermost sampling transects in the Weeki Wachee, Chassahowitzka and Homosassa rivers increased by 33%, 44% and 46%, respectively, between the 1998 to 2000 and 2003 to 2005 sampling periods.

Coincident with the increased nitrogen and phosphorus concentrations and higher nutrient loading rates, were marked declines in submersed aquatic vegetation in each of the three rivers. The Weeki Wachee River exhibited an approximate 75% reduction in mean SAV biomass. A similar reduction was observed in the Homosassa River, i.e. 67%. An approximate 31% reduction in mean SAV biomass was observed in the Chassahowitzka River. Noteworthy is the apparent decline in the frequency of occurrence of native species such as Vallisneria americana in the Homosassa River and Sagittaria kurziana in the Chassahowitzka River. The abundance of periphytonAny organism in a water body, for example a micro alga or diatom, which attaches itself to the bottom (benthic) or to a stem or leaves of a plant either individually or together with others forming a mat.They may be attached or may float free in the water column. The biological community of microscopic plants and animals attached to surfaces in aquatic environments. Algae are the primary component of these asemblages, which naturally reduce phosphorous levels in water to serve a key function in storm water treatment areas. associated with rooted macrophytes increased significantly in both the Homosassa and Chassahowitzka. In fact, mean periphyton abundance on the remnant macrophyte population in the Homosassa was nearly twice as high (85% increase) during the 2003-2005 sampling period than in the 1998-2000 sampling period. In the Chassahowitzka River, the increase in mean periphyton abundance on macrophytes was 30%.

The changes noted above are, in combination, legitimate reasons for concern as noted previously in this report. Increased nutrient delivery, loss of native macrophytes and increased periphyton loads are symptomatic of eutrophication related phenomena. The potential broader consequences of nutrient over-enrichment on the ecological health and integrity of the Weeki Wachee, Chassahowitzka and Homosassa rivers, however, has yet to be fully investigated. We do not know, for example, how changes in the vegetative structure of the rivers may influence the resident faunal communities in these systems. Reductions in submersed aquatic vegetation, which provide both refuge and forage habitats, are likely to significantly alter predator/prey relationships and other important species-level interactions. Such alterations may lead to undesirable shifts in community composition and possibly the loss of key species. Quantitative data on the abundance and distribution of invertebrates and fishes are lacking for the Weeki Wachee, Chassahowitzka and Homosassa rivers and the species/habitat relationships specific to these three systems are, in general, poorly understood. Thus, it is not possible to predict the longer-term effects of nutrient enrichment and resultant decline of submersed aquatic vegetation on the organisms that presently occupy these systems.

Although the focus of this report is appropriately on the Weeki Wachee, Chassahowitzka and Homosassa rivers proper, the potential effects of increased nutrient delivery to their adjacent estuaries and nearshore coastal waters warrants attention as well. Frazer et al. (2006a) have recently documented an increasing trend in surface water chlorophyll concentrations in the estuaries and nearshore coastal waters along the broader Springs Coast region suggestive of an increase in nutrient loading from these and other nearby rivers, e.g., the Crystal and Withlacochee rivers. The potential negative consequences of increased chlorophyll and decreased light availability on the seagrasses and their associated fauna are well documented (see Duarte 1991, Valiela et al 1997) and are of obvious concern (see Frazer et al. 2006a). Clearly, there is a need for a fuller and more quantitative understanding of nutrient loading as it relates to water quality not only in the rivers, but within the broader Springs Coast region.

NOTE: Further details are given in narrative on the pages referring to the particular river (spring run) systems of Citrus County, under these sub-titles: River Description, Temperature, Stream Velocity, Water Depth, Stream Discharge, Stream Discharge, Substrate Type, Light Attenuation, Chemical Parameters: Nitrate, Ammonium, Soluble Reactive Phosphorus, Total Nitrogen, Total Phosphorus, Salinity, Total Alkalinity and pH, Dissolved Oxygen, and Chlorophyll.

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