Corophium alienense

Invasion History

First Non-native North American Tidal Record: 1973
First Non-native West Coast Tidal Record: 1973
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

Corophium alienense was described from specimens collected in 1973 from San Francisco Bay, California (CA). Based on its recent discovery and its close affinity to many corophiids known from the Northwestern Pacific (Japan, China, Vietnam), it is considered a probable introduction to the Northeastern Pacific. So far, it is known only from San Francisco Bay, Tomales Bay, and Bodega Harbor, CA (Chapman 1988; Cohen and Carlton 1995; Bousfield and Hoover 1997; Fairey et al. 2002).

North American Invasion History:

Invasion History on the West Coast:

Corophium alienense was described from specimens collected in 1973 in Corte Madera Creek, San Quentin, on central San Francisco Bay. The recent discovery of the species, its morphological affinities to Asian corophiids, and its abundance marked it as a probable introduction to San Francisco Bay (Chapman 1988). Within the estuary, it is known from the Central Bay, the South Bay, San Pablo Bay, Carquinez Strait, Grizzly Bay, and Suisun Bay. Peterson and Vayssieres (2010) found that it was abundant in dry years in Grizzly Bay in 1977-1986, but remained abundant and dominant in both dry and wet years in 1987-2003, after the invasion of the Asian Brackish-water Clam Corbula amurensis. Corophium alienense was found to be abundant in Tomales Bay in 1993 (Cohen and Carlton 1995) and was subsequently collected in Tomales Bay in 2011 (California Department of Fish and Wildlife 2014). Chapman (2007) mentions its presence in Los Angeles Harbor, but we have not found any specific records for Southern California. Although C. alienensis probably originated from the coast of Southeast Asia, it has not been reported outside of California (Chapman 1988; Bousfield and Hoover 1997; Chapman 2007).

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Description

The estuarine amphipod Corophium alienense is an infaunal amphipod which burrows in muddy sediments. It has a slender, very depressed body, and a massive Antenna 2, which is longer than Antenna 1. The coxal plates are small and separated. The urosome segments are not fused. Both sexes have a pointed rostrum, extending beyond the eye-lobes. The eye is well-developed, but partially obscured by a pigmented cuticle. The first 3 segments of Antenna 1 have long, plumose setae. The 1st segment of the male Antenna 1 lacks a tooth (present in C. heteroceratum). In females, the ventral setae on segments 1-3 are missing. The flagellum has 13-15 segments. Antenna 2 is proportionately larger in males than females, extending well beyond antenna 1. In both sexes, segment 2 bears a large tooth-like excretory spout. In males, segments 4 and 5 of Antenna 2 bear a row of small teeth on the ventral sides. Segment 4 also has a pointed tooth at its distal end. In females, Antenna 2 is only slightly longer than Antenna 1, and lacks the ventral tooth row on segments 4-5, but has a huge distal tooth on segment 4.

The gnathopods are not especially prominent in this genus. Pereiopod 2 is longer than Pereiopod 21 and its dactyl lacks teeth. Pereiopod 7 is nearly twice as long as Pereiopod 6, and has a long curved, smooth, dactyl. The segments of the urosome are separate. Uropod 1 is the longest and 3 is the smallest. The male type specimen was 5.2 mm and the female allotype was 6.4 mm. The centers of the pleonites are mottled brown and white, but the borders, and the appendages are white (photo, in Barnett et al. 2011). Description based on: Chapman 1988, Chapman 2007, and Barnett et al. 2011.

Although C. alienense is known only from San Francisco Bay, Tomales Bay, and Bodega Harbor (Cohen and Carlton 1995; California Department of Fish and Wildlife 2014), it bears a close morphological similarity to Asian species (Chapman 1988; Bousfield and Hoover 1997). Bousfield and Hoover (1997) placed it in the genus Sinocorophium, together with eight Asian species. John Chapman considers the genus Sinocorophium (Bousfield and Hoover 1997) indistinct from Corophium, and thus invalid (Chapman 2007; John Chapman, personal communication).

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Taxonomy

Ecology

General:

Corophium alienense is a tube-building gammarid amphipod, so far only known from California estuaries (Chapman 1988; Cohen and Carlton 1995; Graening et al. 2012). Gammarid amphipods have separate sexes, brooded embryos, and direct development (Bousfield 1973). We have no specific information on the life history of C. alienense. Nocturnal migration is common in the genus (Chapman 1988).

Corophium alienense is tolerant of a wide range of temperature and salinity, and has been collected in marsh pools at a temperature of 30C (Chapman 2007). It ranges into low-salinity waters in Suisun Bay and the Napa River (Cohen and Carlton 1995; Lee et al. 2003; Peterson and Vaysierres 2010). Corophium alienense builds U-shaped tubes in shallow subtidal and intertidal muddy sand (Chapman 1988; Graening et al. 2012). This amphipod is an abundant member of the epifauna on Eelgrass (Zostera marina) in San Francisco Bay (Carr et al. 2011). Corophium alienense is a suspension-feeder, and surface-deposit-feeder. It is considered a significant grazer in brackish tributaries of San Francisco Bay (Jones et al. 2009; Barnett et al. 2011). Fishes are the primary predators of benthic amphipods in these estuaries (Feyrer et al. 2003).

Food:

Detritus; Phytyoplankton

Trophic Status:

Deposit Suspension Feeder

DepSusFed

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Habitats

General Habitat	Unstructured Bottom	None
General Habitat	Grass Bed	None
Salinity Range	Limnetic	0-0.5 PSU
Salinity Range	Oligohaline	0.5-5 PSU
Salinity Range	Mesohaline	5-18 PSU
Salinity Range	Polyhaline	18-30 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None
Vertical Habitat	Endobenthic	None

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Life History

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Tolerances and Life History Parameters

Minimum Temperature (ºC)	30	Field (Chapman 2007)
Minimum Salinity (‰)	0.7	Field, mean salinity, Fresh-Brackish-Muddy zone, San Francisco Delta (Lee et al. 2003)
Maximum Salinity (‰)	27.5	Field, mean salinity, Marine-Muddy zone, South and Central San Francisco Bay (Lee et al. 2003)
Maximum Length (mm)	6.4	Adult female (Chapman 1988)
Broad Temperature Range	None	Warm temperate
Broad Salinity Range	None	Tidal Limnetic-Polyhaline

General Impacts

Corophium alienense is one of the dominant benthic organisms in brackish tributaries of San Francisco Bay. It increased in abundance after the invasion of the Asian Brackish-water Clam (Corbula amurensis) (Peterson and Vayssieres 2010). In Suisun Slough, the estimated grazing rate of C. alienense was ~15X greater than that of C. amurensis. However, the rate of phytoplankton loss due to grazing was much smaller than the loss by sedimentation, which was attributed to a flocculent surface layer of mucus, to which the tubes of C. alienense contributed, along with many other benthic organisms (Jones et al. 2009). Tube-building amphipods, including C. alienense, are important food items for native and introduced benthic-feeding fishes in San Francisco Bay (Feyrer et al. 2003).

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Regional Impacts

NEP-V	Northern California to Mid Channel Islands		Ecological Impact	Habitat Change
In Suisun Slough, mucus from the tubes of C. alienense as well as the mucus produced by other native and introduced deposit feeding and tube-building benthos, contributes to a surface layer of flocculent fluff, which may trap much more phytoplankton than that actually consumed by the animals (Jones et al. 2009).
P090	San Francisco Bay		Ecological Impact	Habitat Change
In Suisun Slough, mucus from the tubes of C. alienense as well as the mucus produced by other native and introduced deposit feeding and tube-building benthos, contributes to a surface layer of flocculent fluff, which may trap much more phytoplankton than that actually consumed by the animals (Jones et al. 2009).
P090	San Francisco Bay		Ecological Impact	Herbivory
Corophium alienense is a significant suspension-feeder in the benthos of Suisun Slough, and other brackish San Francisco Bay tributaries. Specific grazing rates for the population were estimated from those of the similar Atlantic amphipod C. volutator, as 9 m-3 . m-2 . day-1, for the populaiton about 15X higher than that of the Asian Brackish-Water Clam ( Corbula amurensis) population (Jones et al. 2009). This estimate makes it the major suspension-feeder in this part of the San Francisco estuary.
NEP-V	Northern California to Mid Channel Islands		Ecological Impact	Herbivory
Corophium alienense is a significant suspension-feeder in the benthos of Suisun Slough, and other brackish San Francisco Bay tributaries. Specific grazing rates for the population were estimated from those of the similar Atlantic amphipod C. volutator, as 9 m-3 . m-2 . day-1, for the populaiton about 15X higher than that of the Asian Brackish-Water Clam (Corbula amurensis) population (Jones et al. 2009). This estimate makes it the major suspension-feeder in this part of the San Francisco estuary.
P090	San Francisco Bay		Ecological Impact	Food/Prey
Tube-dwelling and free-living gammarid amphipods were important food items for several native (Tule Perch- Hysterocarpus traskii, Prickly Sculpin- Cottus asper, Starry Flounder- Platichthys stellatus) and introduced fishes (Acanthogobius longimanus, Yellowfin Goby) (Feyrer et al. 2003).
NEP-V	Northern California to Mid Channel Islands		Ecological Impact	Food/Prey
Tube-dwelling and free-living gammarid amphipods were important food items for several native (Tule Perch- Hysterocarpus traskii, Prickly Sculpin- Cottus asper, Starry Flounder- Platichthys stellatus) and introduced fishes (Acanthogobius longimanus, Yellowfin Goby) (Feyrer et al. 2003).
CA	California		Ecological Impact	Food/Prey
Tube-dwelling and free-living gammarid amphipods were important food items for several native (Tule Perch- Hysterocarpus traskii, Prickly Sculpin- Cottus asper, Starry Flounder- Platichthys stellatus) and introduced fishes (Acanthogobius longimanus, Yellowfin Goby) (Feyrer et al. 2003)., Tube-dwelling and free-living gammarid amphipods were important food items for several native (Tule Perch- Hysterocarpus traskii, Prickly Sculpin- Cottus asper, Starry Flounder- Platichthys stellatus) and introduced fishes (Acanthogobius longimanus, Yellowfin Goby) (Feyrer et al. 2003).
CA	California		Ecological Impact	Habitat Change
In Suisun Slough, mucus from the tubes of C. alienense as well as the mucus produced by other native and introduced deposit feeding and tube-building benthos, contributes to a surface layer of flocculent fluff, which may trap much more phytoplankton than that actually consumed by the animals (Jones et al. 2009)., In Suisun Slough, mucus from the tubes of C. alienense as well as the mucus produced by other native and introduced deposit feeding and tube-building benthos, contributes to a surface layer of flocculent fluff, which may trap much more phytoplankton than that actually consumed by the animals (Jones et al. 2009).
CA	California		Ecological Impact	Herbivory
Corophium alienense is a significant suspension-feeder in the benthos of Suisun Slough, and other brackish San Francisco Bay tributaries. Specific grazing rates for the population were estimated from those of the similar Atlantic amphipod C. volutator, as 9 m-3 . m-2 . day-1, for the populaiton about 15X higher than that of the Asian Brackish-Water Clam (Corbula amurensis) population (Jones et al. 2009). This estimate makes it the major suspension-feeder in this part of the San Francisco estuary., Corophium alienense is a significant suspension-feeder in the benthos of Suisun Slough, and other brackish San Francisco Bay tributaries. Specific grazing rates for the population were estimated from those of the similar Atlantic amphipod C. volutator, as 9 m-3 . m-2 . day-1, for the populaiton about 15X higher than that of the Asian Brackish-Water Clam ( Corbula amurensis) population (Jones et al. 2009). This estimate makes it the major suspension-feeder in this part of the San Francisco estuary.

References

Barnett, Rachel; Bell, Sabrina; Floerke, Wyatt; Templin, Bill (2011) <missing title>, California Interagency Ecological Program, Sacramento CA. Pp. 13

Bousfield, E. L.; Hoover, P. M. (1997) The amphipod superfamily Corophioidea on the Pacific coast of North America. Part V. Family Corophiidae: Corophiinae, new subfamily. Systematics and distributional ecology., Amphipacifica 2(3): 67-139

Bousfield, E.L. (1973) <missing title>, Comstock Publishing Associates, Ithaca, NY. Pp. <missing location>

California Department of Fish and Wildlife (2014) Introduced Aquatic Species in California Bays and Harbors, 2011 Survey, California Department of Fish and Wildlife, Sacramento CA. Pp. 1-36

Carr, Lindsey A.; Boyer, Katharyn E.; Brooks, Andrew J. (2011) Spatial patterns of epifaunal communities in San Francisco Bay eelgrass (Zostera marina) beds, Marine Ecology 32: 88-103

Chapman, John W. (1988) Invasions of the Northeast Pacific by Asian and Atlantic Gammaridean amphipod crustaceans, including a new species of Corophium, Journal of Crustacean Biology 8(3): 364-382

Chapman, John W. (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California Press, Berkeley CA. Pp. 545-611

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Fairey, Russell; Dunn, Roslyn; Sigala, Marco; Oliver, John (2002) Introduced aquatic species in California's coastal waters: Final Report, California Department of Fish and Game, Sacramento. Pp. <missing location>

Feyrer, Frederick; Herbold, Bruce; Matern, Scott A.; Moyle, Peter (2003) Dietary shifts in a stressed fish assemblage: consequences of a bivalve invasion in the San Francisco estuary., Environmental Biology of Fishes 67: 277-288

Feyrer, Frederick; Sommer, Ted; Slater, Steven B. (2009) Old school vs. new school: status of threadfin shad (Dorosoma petenense) five decades after its introduction to the Sacramento-San Joaquin Delta, San Francisco Estuary and Watershed Science 7(1): published online

Graening, G. O.; Rogers, D. Christopher; Holsinger, John R.; Barr, Cheryl; Bottorff, Richard (2012) Checklist of inland aquatic Amphipoda (Crustacea: Malacostraca) of California, Zootaxa 3544: 1-27

Howe, Emily R.; Simenstad, Charles A.; Toft, Jason D.; Cordell, Jeffrey R.; Bollens, Stephen M. (2014) Macroinvertebrate prey availability and fish diet selectivity in relation to environmental variables in natural and restoring North San Francisco Bay tidal marsh channels, San Francisco Estuary and Watershed Science 12(1): 1-46

Jones, Nicole L.; Thompson, Janet K.; Arrigo, Kevin R.; Monismith, Stephen G. (2009) Hydrodynamic control of phytoplankton loss to the benthos in an estuarine environment, Limnology and Oceanography 54(3): 952-969

Lee, Henry II; Thompson, Bruce; Lowe, Sarah (2003) Estuarine and scalar patterns of invasion in the soft-bottom benthic communities of the San Francisco estuary., Biological Invasions 5: 85-102

Peterson, Heather A.; Vayssieres, Marc (2010) Benthic assemblage variability in the upper San Francisco estuary: A 27-year retrospective, San Francisco Estuary and Watershed Science <missing volume>: published online

Robinson, April; Cohen, Andrew N.; Lindsey, Brie; Grenier, Letitia (2011) Distribution of macroinvertebrates across a tidal gradient, Marin County, California, San Francisco Estuary and Watershed Science 9(3): published online

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