See Czaika (1982) for a key to naupliar stages.

Population peaks are present at different times of year in different regions of the world. In the Milwaukee Harbor, it is present from July to November but absent in winter and spring, while in the northern Baltic Sea it is known to overwinter at low population density. In the Atchafalaya River system in Louisiana it occurs at its highest abundance in early summer, while in two European estuaries, the Gironde and the Westerschelde, it is dominant in winter and spring. In a Scottish estuary, the Forth, it is dominant in winter and summer (Roddie et al. 1984; Tackx et al. 1995; Davidson et al. 1998; Katajisto et al. 1998; Torke 2001).

Eurytemora affinis is epibenthic, inhabiting both the sediments and the water column in Lake Michigan, where it is often particularly abundant in the first 10 m of water. In this lake, abundance in the water column is significantly higher in the day than at night in June, and then evens out later in the summer. In Lake Michigan, the presence of E. affinis in sediments increases in late summer. It spends winter and spring as eggs (Wells 1970; Nalepa and Quigley 1985).

Eurytemora affinis can tolerate salinities of 0–40%. In Chesapeake Bay, it is most abundant in waters of 5–10ºC and salinities of 3–8% but can tolerate higher salinities at lower temperatures. High salinities at high temperatures are stressful. Experiments indicate that optimum temperature and salinity ranges for this species are 10–15ºC and 5–15% respectively. Interestingly, one Japanese experiment showed that individuals introduced to freshwater from a brackish water source are still best adapted to salinities of 5–15%, and that eggs from this population hatch well at salinities of 0–20%. Eurytemora affinis can tolerate high turbidity, although production may decrease due to low food availability from lack of light and difficulty in selecting edible particles. In some European estuaries, this species is considered limited by high turbidity and anoxia (Sautour and Castel 1995; Burdloff et al. 2000; Kimmel and Bradley 2001; Roman et al. 2001; Seuront 2006).

Eurytemora affinis grazes on algae, bacteria, organic detritus and protozoans, including ciliates and dinoflagellates. It can increase feeding on heterotrophic plankton rather than autotrophic plankton when suspended particulate matter increases in concentration. Feeding on microplankton ciliates is most efficient due to better perception, handling, and relative nutritional quality of these larger food particles in comparison to phytoplankton (Gasparini and Castel 1997; Merrell and Stoecker 1998; Torke 2001; David et al. 2006).

Summary of species impacts derived from literature review. Click on an icon to find out more...

Environmental

Potential:
Eurytemora affinis has the ability to feed on toxic cyanobacteria and dinoflagellates (Dinophysis spp.) (Engström et al. 2000, Setälä et al. 2009). While these do not appear to be their preferred food source, consumption of toxic phytoplankton results in the buildup of toxins in zooplankton tissue and feces, which consequently can accumulate in benthic organisms, fish, and organisms further up the food chain (Engström et al. 2000, Lehtiniemi et al. 2002, Setälä et al. 2009). Copepods are also common hosts for fish parasites (Piasecki et al. 2004). In particular, E. affinis is a probable host and vector for plerocercoids that can infect striped bass in the Sacramento-San Joaquin Estuary (Arnold and Yue 1997).

Mesocosm experiments indicate that E. affinis has the potential to control some populations of protozoan ciliates and rotifers when these prey items are found at high densities (Feike and Heerkloss 2009, Merrell and Stoecker 1998). Because E. affinis has become an abundant grazer in parts of the Great Lakes, it is possible that it has had important impacts on the food web—both adverse and beneficial (see below) (Lee et al. 2007).

Current research on the socio-economic impact of Eurytemora affinis in the Great Lakes is inadequate to support proper assessment.

Potential:
Outbreaks of cholera are sometimes correlated with copepods, which are common hosts of Vibrio cholerae (Colwell 2004, Lee et al. 2007, Piasecki et al. 2004). Cholera outbreaks tend to be associated with algal blooms and the rapid increase in copepods that follows (Piasecki et al. 2004). Eurytemora spp. are known to host V. cholerae and are the most common of known copepod hosts in the Chesapeake Bay, where this has been studied (Colwell 2004).

Eurytemora affinis has the ability to consume cyanobacteria and other toxic algal blooms; studies in the Baltic Sea indicate that this is likely an important mechanism of the biomagnification of toxins in organisms of economic importance, such as shrimp and fish (Engström et al. 2000, Karjalainen et al. 2008, Setälä et al. 2009).

There is little or no evidence to support that Eurytemora affinis has significant beneficial effects in the Great Lakes.

Potential:
Eurytemora affinis could be a significant prey item for fish and other planktivores. Thorp and Casper (2003) demonstrated such potential in an enclosure experiment with yellow perch (Perca flavescens) in the St. Lawrence River; 99% of E. affinis disappeared from fish enclosures, presumably due to predation.

Note: Check federal, state/provincial, and local regulations for the most up-to-date information.

Control
Biological
Maes et al. (2005) found that juvenile herring (Clupea harengus) and sprat (Sprattus sprattus) exhibit top down control of Eurytemora affinis through predation pressure in the Scheldt estuary in Belgium.

Physical
There are no known physical control methods for this species.

Chemical
The Great Lakes and Mississippi River Interbasin Study (GLMRIS 2012) suggests that alteration of water quality using carbon dioxide, ozone, nitrogen, and/or sodium thiosulfate could be effective in preventing upstream and downstream movement of copepods. It should be noted that the effectiveness of these methods is likely significantly diminished against copepod ephippia.

Lindley et. al (1999) found that exposure to the organochlorine compounds pentachlorophenol (PCP) and 1, 2-dichlorobenzene (DCB), (both common industrial pollutants) accumulated in sediment significantly reduced hatching success and nauplii viability of E. affinis eggs. In a study of the effect of salinity on toxicity of cadmium to Chesapeake Bay organisms, Hall Jr. et al. (1995) found that E. affinis is very sensitive to cadmium compared to other estuarine aquatic biota. The study documents 96 h LC50 (lethal concentration to 50% of organisms tested) values of 51.6, 213.2, and 82.9 µg L-1 at 5, 15, and 25 ppt (parts per thousand) salinities, respectively (Hall Jr. et al. 1995). Sullivan et al. observed a 96 h LC50 of >120 µg L-1 for cadmium and ~30 µg L-1 for copper on E. affinis at 10 ppt salinity (1983). Sullivan et al. (1983) also noted that reduced growth rates of E. affinis occur at Cu and Cd doses below the 96 h LC50, which has been documented as extending generation length and eventually reducing population size in previous studies. The negative effects of the insecticide diflubenzuron (Dimilin®) on E. affinis nauplii were documented by Savitz and Wright, who noted a 48 h LC50 of 2.2 µg L-1. The insecticide is approved for use against the gypsy moth (Lymantria dispar) and other insect pests by the US EPA, and enters E. affinis habitat through runoff or by direct spraying (Savitz and Wright 1994). Diflubenzuron specifically targets the arthropod molting process, so the most explicit effects are expected in sub-adult crustaceans. E. affinis was lethally affected at levels as low as 0.78 µg L-1 (Savitz and Wright 1994).

Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.

Euryhaline species, found in estuaries, saltmarshes, brackish waters and freshwater lakes, ponds and reservoirs. Planktonic or epibenthic grazer, feeding on plankton and organic detritus; females can produce multiple clutches of eggs; overwinters as eggs, juveniles and adult stages found between April and January.

Frequently exhibits both vertical and horizontal migrations. Vertical migrations may occur in response to fluctuations in salinity, over day-night cycles, and over tidal cycles. They often occur more frequently in lakes than swamps or channels. Horizontal migrations between nearshore and open water areas may occur over day-night cycles and migrations from one habitat type to another may occur in response to oxygen regimes. In tidal areas, E. affinis is most active during the flood of spring tides and the ebb of neap tides (Hough and Naylor 1992; Morgan et al. 1997; Appeltans et al. 2003; Kelso et al. 2003; Jack et al. 2006; Seuront 2006).