4.3. Macroinvertebrates

4.3.1. Description

Benthic macroinvertebrates include invertebrates (animals without a backbone) that live on or in the sediment and can be seen with the naked eye. They include a large variety of organisms such as sponges, crabs, shrimp, clams, oysters, barnacles, insect larvae, and worms. Almost 400 species from 10 phyla have been identified in the LSJRB. Sponges (Phylum Porifera)

Sponge. Photo by Kimberly Mann

Sponges are stationary filter feeding organisms consisting of over 5,000 species with about 150 freshwater species. They do not have organs or tissues, but the cells specialize in different functions. They reproduce both sexually and asexually (Myers 2001c). In the LSJRB, five taxa have been recorded and are found in fresh, marine, and estuarine waters (i.e., Spongilla fragilis and Craniella laminaris) (Mattson, et al. 2012). Sea Stars and Sea Cucumbers (Phylum Echinodermata)

Brittle Star
Brittle Star (Family Ophioderma)
Photo by Christina Adams.
Sea cucumber
Brittle Star (Family Ophioderma)
Photo by Christina Adams.

There are approximately 7000 marine species. They can range in size from 1 cm to 2 m. Food habits vary among the different species, anything from filter feeders to scavengers to predators. Sea stars can regenerate missing arms, and sea cucumbers and urchins are also able to regenerate certain parts of their anatomy (Mulcrone 2005). “Moss Animals” (Phylum Bryozoa)

Genus Bugula
Genus Bugula from http://www.serc.si.edu

This group of animals lives in colonies (Collins 1999). They have tentacles which they use to filter phytoplankton out of the water (Bullivant 1968). Five non-native species have been recorded in the LSJRB (see Section 4.5 Non-native Aquatic Species; Mattson, et al. 2012). Jellyfish, Sea Anemones, and Hydrozoans (Phylum Cnidaria)

Tubularian Hydroid
Tubularian Hydroid (Tubularia crocea)
Photo by Bob Michelson from http://stellwagen.noaa.gov
Sea anemone
Sea Anemone (Order Actiniaria) from http://digitalmedia.fws.gov
Jellyfish (Class Scyphozoa) from

All the species in this phylum have stinging cells called nematocysts. They have two basic body forms – medusa and polyp. Medusae are the free-moving, floating organisms, such as jellyfish. Polyps are benthic organisms such as the hydrozoans (Myers 2001a). In the LSJRB, hydrozoans are more common than jellyfish and sea anemones. Eight taxa have been recorded in the LSJRB, with three taxa found in freshwater including Corylophora lacustris (Mattson, et al. 2012). The non-native freshwater jellyfish Craspedacusta sowerbyi has been recorded in the LSJRB (see Section 4.5 Non-native Aquatic Species). Ribbon Worms (Phylum Nemertea)

Ribbon Worm
Ribbon Worm (Genus Tubulanus)
Photo by Kare Telnes from http://www.seawater.no/fauna/nemertea/

The common name “ribbon worm” relates to the length of many species with one species being   30 m. Marine species are more common than freshwater species (Collins 2001). Besides long length, these worms have an elongated appendage from the head called a proboscis that they use to capture prey. (Collins 2001; Graf 2013). One ribbon worm was recorded by Evans, et al. 2004 that was salt and pollution tolerant. Snails, Mussels, and Clams (Phylum Mollusca)

Snails (Class Gastropoda)
Photo by Kimberly Mann
American Oyster
American oyster (Crassotrea virginica)
Photo by Kimberly Mann
Mussel (Class Bivalvia) from http://digitalmedia.fws.gov

The Mollusca are very diverse with >50,000 species, ranging in size from less than a millimeter to more than twenty meters long (giant squids). Over 150 taxa have been identified in the SJRB, including more than 3 invasive taxa (see Section 4.5 Non-native Aquatic Species) and others endemic to the SJR drainage (Elimia sp.) (Mattson, et al. 2012). Representative taxa include Mytilopsis leucophaeata, Gemma gemma, Littoridinops, Boonea impressa, Nassarius obsoletus, and the non-native Rangia cuneata (Cooksey and Hyland 2007). Six taxa were recorded by Evans, et al. 2004 from 2002-2003 collections in the LSJRB. Each taxon was pollution tolerant and two taxa were gastropods and the other four were bivalves. “Peanut Worms” (Phylum Sipuncula)

Peanut Worm
Peanut Worm (Phylum Sipuncula) from http://www.ucmp.berkeley.edu

The common name “peanut worm” relates to their shape. Over 320 marine species have been described and they are found in sand, mud, and crevices in rocks and shells (Collins 2000). “Horseshoe worm” (Phylum Phoronida)

Horseshoe Worm
Genus Phononpsis, Copyright Peter Wirtz peterwirtz2004@yahoo.com

Approximately 12 marine species have been identified with some species having horseshoe-shaped tentacles (Collins 1995). They are most common in shallow sediments. Phoronis has been recorded from Clapboard Creek (Cooksey and Hyland 2007). Insect larvae (Phylum Arthropoda, Supbphylum Crustacea, Class Insecta)

Insect Larvae
Insect larvae (Class Insecta) from http://digitalmedia.fws.gov

Most insect larval forms look differently from their adult stage. Those larvae associated with aquatic habitats can be found under rocks and in the mud (Myers 2001b). Representative genera include Coelonypus and Chrionomus (Cooksey and Hyland 2007). Sixteen taxa were recorded by Evans, et al. 2004 from 2002-2003 collections in the LSJRB. These taxa were found in freshwater, and six were pollution tolerant. Isopods, Amphiphods, and “shrimp-like” crustaceans (Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, Superorder Peracarida)

Amphipod, photo by A. Slotwinkski, from http://www.imas.utas.edu.au
Isopod, photo by A. Slotwinski, from http://www.imas.utas.edu.au
Mysid (“shrimp-like”), photo by A. Slotwinski, from http://www.imas.utas.edu.au

It has been estimated that there are over 54,000 species in this group (Kensley 1998).  They all possess a single pair of appendages (maxillipeds) extending from their chest (thorax) and mandibles. The maxillipeds assist in getting food to their mouth. For this superorder, the carapace (the exoskeleton protecting the head and some to all of the thorax is reduced in size and does not cover all of the thorax. The carapace is also used to brood eggs (UTAS 2013). Over 60 taxa have been recorded in the LSJRB (Mattson, et al. 2012). In the LSJRB, eleven taxa were recorded, of which all were salt-tolerant, and four taxa were pollution-intolerant (Evans, et al. 2004). Example taxa are Paracaprella pusilla, Apocorophium lacustre, and Protohaustroius wigleyi (Cooksey and Hyland 2007). Two species are non-native to the SJRB (see Section 4.5 Non-native Aquatic Species). Crabs and Shrimp (Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, Order Decapoda)

Blue Crab
Blue Crab (Callinectes sapidus) from http://digitalmedia.fws.gov
Shrimp (Order Decapoda)
Photo by Kimberly Mann

This is one of the most well-known groups since many people eat crabs, shrimps, and lobsters. Decapoda refers to the five pairs of legs. This group has an exoskeleton, which they periodically have to shed (molt) so they can continue to grow. Their body is divided into three sections – the head, thorax and abdomen. The head and thorax are fused together and covered by the carapace. In crabs, the abdomen is curved under the carapace (Humann and Deloach 2011). Approximately 55 taxa of crabs and shrimp have been reported in estuarine, marine, and freshwater in the LSJRB (Appendix 3.3.2a-3.3.3b). In the SJRB, five species are commercially and/or recreationally (Mattson, et al. 2012) harvested. In 2002-3, Evans, et al. 2004 recorded two taxa in salt waters, of which Rhithropanopeus harrisii was pollution intolerant. Four species are non-native to the SJRB (see Section 4.5 Non-native Aquatic Species). Barnacles (Phylum Arthropoda, Subphylum Crustacea, Class Malacostraca, Infraclass Cirripedia)

Gooseneck Barnacles
Gooseneck Barnacles, http://www.digitalmedia.fws.gov

There are approximately over 1,400 species. Size can range from a few centimeters to slightly greater than 10 cm. Barnacles are attached to a hard substrate or other organisms. The carapace completely encloses their soft body. They do not possess compound eyes or appendages. For most, their habitat is along rocky shoreline in the intertidal zone (Newman and Abbott 1980). Two taxa were recorded by Evans, et al. 2004 that were salt and pollution tolerant in the LSJRB. Five non-native taxa have been recorded in the LSJRB (see Section 4.5 Non-native Aquatic Species). Worms (Class Polychaeta, Phylum Annelida)

Limnodrilus Hoffmeisteri
Limnodrilus hoffmeisteri (Subclass Oligochaeta) from http://www.fcps.edu
Class Polychaete
Class Polychaete,
Photo by Kimberly Mann

This phylum consists of worms that have segmented bodies, including earthworms. Polychaete means “many bristles” and members of this class look like feathered worms. Over 200 taxa have been recorded in the SJRB (Mattson, et al. 2012). Example taxa are Streblospio benedicti, Mediomastus, Neanthes succinea, Nereis, Sabellaria vulgaris, Paraonis fulgens, Nephtys picta (Cooksey and Hyland 2007). Streblospio benedicti and N. succinea are pollution tolerant and representative of impaired environmental conditions (Cooksey and Hyland 2007). Seventeen taxa were recorded by Evans, et al. 2004, of which two taxa were pollution intolerant (Orginiidae sp. and Scolopolos rubra) and another two species that were freshwater tolerant (Aulodrilus pigueti and Limnodrilus hoffmeisteri) (Evans, et al. 2004).

4.3.2. Significance

Benthic macroinvertebrates are an important component of the river’s food web. Indeed, many of the adults of these species serve as food for commercially and recreationally important fish and invertebrate species. Their microscopic young can also be very abundant, providing food resources for smaller organisms, such as important larval and juvenile fish species. Benthic activities in the sediment or bioturbation can result in sediment turnover, changes in oxygen and nutrient availability, and distribution of grain size. The presence of stress-tolerant species can serve as an indicator of river health (Table 4.3; Pearson and Rosenberg 1978; Gray, et al. 1979). For more information on pollution in benthic invertebrates, see Section 5 Contaminants.

4.3.3. Data Sources

Macroinvertebrate community data used to assess long-term trends were obtained from the Florida Department of Environmental Protection (DEP), Florida’s Inshore Marine and Assessment Program (IMAP), and the St. Johns River Water Management District (SJRWMD). The primary data set (1973-2000) was provided courtesy of the Jacksonville DEP office. Supplemental data from DEP’s “Fifth Year Assessments” were obtained online (DEP 2013m). Data sets were combined to increase the temporal strength of the analyses. In an attempt to limit bias in community information only data collect via sediment grabs (Ponar, Ekman, and Young modified Van Veen grabs) were used for data up to 2000. Due to the scarceness of data after 2000, dip net sweeps were included from 2001 to present. Macroinvertebrates were assessed in conjunction with the three ecological zones based on salinity differences.

4.3.4. Limitations

While the dataset encompasses 30 years, similar regions were not sampled throughout the entire time period, different collection methods were used, and sample size was either unequal or insufficient given natural variability. The freshwater lacustrine zone (FLZ) was visited the least with an average of three samples per year. Comparing collections from earlier samples that used mostly petite Ponar grabs with those of more recent collections that used mostly Young modified Van Veen grabs or dipnets is problematic. The dataset assesses macroinvertebrates in deeper sections of the river, because sampling did not occur in shallow areas where boat access was prohibitive.

4.3.5. Current Status (UNCERTAIN)

The current status is rated as UNCERTAIN. Evidence of shifts from low-salinity, pollution-sensitive taxa to higher-salinity, pollution-tolerant taxa at a site where Sisters Creek meets Ft. George River (Evans, et al. 2004; Hymel 2009). Evans, et al. 2004; Hymel 2009 reported occurrences of larval deformity from 20 sites in the LSJRB. Abundance of pollution tolerant taxa and presence of deformities were recorded at severely to very severely impaired sites, Cedar River, Julington Creek, Goodbys Creek, and Trout River (Table 4.9). Deformities of Chironomus and Coelotanypus larvae can be due to metals, such as lead and copper, organic compounds. Impairment of these sites may be due to low dissolved oxygen, toxic compounds, nutrient loading, and/or poor quality of sediment (Evans, et al. 2004; Hymel 2009).

Table 4.9 Percentage of pollution and salt tolerant invertebrates and numbers of deformities in the LSJR (Source: Evans, et al. 2004).
TOLERANT TAXA 2001, 2002/3
# Occurrence of deformities (number of deformities) 2002/3# Taxa and density of individuals
Arlington River100
Cedar Creek81
Green Cove Springs74, 7633Coelotanypus 0 (0)6 taxa
356 individuals/m2
Rice Creek14-86
Julington Creek100, 9348Coelotanypus 100 (12)7 taxa present
453 individuals/m2
Ortega River77-100
Goodbys Creek97-99, 346Coelotanypus 1004 (4)10 taxa present
346 individuals/m2
Cedar River99-100
Trout River100, 9680Polypedilum halterale griseopunctatum 0 (1)6 taxa present
269 individuals/m2
Doctor's Lake-, 100100Absent1 taxon present
356 individuals/m2
Clapboard Creek-, 82100Absent15 taxa present
896 individuals/m2

Benthic macroinvertebrate assemblages change from the saltwater dominated mesohaline riverine zone (MRZ) to the freshwater areas of the freshwater lacustrine zone (FLZ) (Mason Jr 1998; Evans and Higman 2001; Vittor 2001; Vittor 2003; Evans, et al. 2004; Cooksey and Hyland 2007; Figure 4.8; for a complete list of species, see Appendix 4.3.6). As stated in Section 2.8, the mesohaline riverine zone is 40 km long running from Mayport Inlet to the Fuller Warren Bridge with an average salinity of 14.5 psu. The oligohaline lacustrine zone (OLZ) has an average salinity of 2.9 psu and encompasses the area from the Fuller Warren Bridge, 35 miles along the river to Doctors Lake. The two northern zones were dominated by annelids, the MRZ by polychaetes, and the OLZ by oligochaetes (Table 4.10). In addition, the MRZ had a high percentage of amphipods and isopods, the OLZ with molluscs, and the FLZ with insect larvae. In the 1970s, the MRZ was dominated by barnacles and the amphipod group, the OLZ by mussels and the FLZ by insect larvae (Figure 4.8). In the 1990s, polychaetes were abundant as compared to barnacles in the MRZ, isopods were more abundant in the OLZ, and mussels were more abundant in the FLZ (Figure 4.8).

4.3.6. Trend (UNCERTAIN)

Community shifts are expected in response to the natural changes in water quality, salinity, and temperature in addition to biological factors that can include recruitment and predation variability (Cooksey and Hyland 2007). It is important to recognize that the mechanism by which many of these organisms may be affected is by either direct impact to adults or to the offspring that spend part of their time in the water column as plankton. During the planktonic stage of these organisms lives, environmental gradients (i.e., salinity, temperature, dissolved oxygen) within the river can affect where young are and how they are transported to adult habitat.

The current trend is rated as UNCERTAIN. The lack of recent surveys and monitoring of benthic macroinvertebrates makes it difficult to identify trends, especially since microhabitat variability can be as high as site variability. Yet, low species richness, diversity, and abundance are representative of impaired benthic conditions (Cooksey and Hyland 2007). The health of the SJR is linked to the health of benthic macroinvertebrates. A potential concern is if macroinvertebrate communities change in a large area within the river, and then affect abundances of ecologically, commercially or recreationally important species (for example, red drum, spotted sea trout, or flounder).

Gross and Burgess 2015 assessed Rice Creek and main channel macroinvertebrate communities from 2010 to 2014 following relocation of GP Palatka Mill discharge pipe. Macroinvertebrate abundance increased and macroinvertebrate diversity decreased at littoral sites and basin-wide sites within the stretch 10 km north and south of the discharge relocation. They suggested that discharge relocation resulted in successful restoration and reported differences in abundance and diversity may be a function of rainfall patterns and other basin-wide factors (Gross and Burgess 2015).

During the study period, caddisfly (aquatic insects intolerant to pollution) decreased in littoral sites 10 km south of the discharge relocation (Gross and Burgess, unpubl data). Comparing July samples when caddisfly were typically most abundant, densities reached, on average, 26 individuals per Hester Dendy artificial substrate device located along wooded banks in 2010 and 2011, 7-10 km south of Rice Creek, but were not recorded in 2013 and 2014. By comparison, 7-10 km north of Rice Creek, numbers were less than 2 individuals per device, on average, and only recorded in July 2010 and 2012. However, caddisfly individuals were recorded at the mouth of Rice Creek throughout the study, excepting July 2012 (Gross and Burgess, unpubl data). As indicators of good water quality, the absence of caddisfly 10 km south of Rice Creek in the latter years and generally low densities 10 km north of Rice Creek may warrant further investigation. A trend of decreasing aquatic insects has also been observed since the 1970s (Figure 4.8).

Table 4.10 Common macroinvertabrate taxa in LSJR.
Tidal freshwater/upper oligohalineFreshwater
Aquatic insect
Isopod Cyathura polita
Mysid Mysidopsis almyra
Aquatic insect Chironomus plumosus, C. decorus, Glyptotendipes lobiferus, Callibaetis floridanus, Stenacron floridense, Oecetis, Hydroptila, Orthotrichia, Cyrnellus fraternus, Lype diversa
Cichra 1998; Mason Jr 1998
Lower oligohaline/upper mesohalineEstuarine
Aquatic insect
Polychaete Streblospio bendicti, Marenzelleria viridis, Limnodrilus hoffmeisteri, Questridilus multisetosus
Amphipod Corophium, Hartmanodes nyei, Gammarus
Decapod R. leucophaeata
Snail Littoridinops monroensis
Gastropod Physa, Amnicola, Littoridinops
Bivalve Corbicula fluminea, Rangia cuneata, Mytilopsis leucophaeata, Ischaedium recurvum, Macoma mitchelli
Barnacle Ischadium recurvum
Aquatic insect Coelotanypus, Chironomus plumosus, Glyptotendipes lobiferus
Cichra 1998; Mason Jr 1998; Cooksey and Hyland 2007
Lower mesohaline/polyhalineEstuarine, marine
Bivalve Tellina, Macoma tenta, Mytilopsis leucophaeta, Ischadium recurvum, Mulinia lateralis, Boonea impressa, Gemma gemma
Polychaete Capitella capitata, Mediomastus californiensis, S. benedictii, Neanthes succinea, Nereis, Sabellaria vulgaris, Paranois fulgens, Nephtys picta
Amphipod Protohaustroius wigleyi
Oligochaete Tubificoides heterochaetus
Crustacean Apocorphium lacustre
Cooksey and Hyland 2007; Banks 2015
Figure 4.8
Figure 4.8 Percent of macroinvertebrate present each decade in the three ecological zones of the Lower Basin of the St. Johns River from the 1970s to 2000. The meso polyhaline riverine zone is dominated by barnacles, polychaete worms, and isopods/amphipods. Insect larva and oligochaete worms dominate the freshwater lacustrine zone with mussels gaining influence in the 1990s and 2000s. The oligohaline lacustrine zone reflects its transition between salinity and freshwater by being dominated by mussels and worms, both polychaetes and oligochaete (Mason Jr 1998; Evans and Higman 2001; Vittor 2001; Vittor 2003; Evans, et al. 2004; Cooksey and Hyland 2007).