More Information about Benthic Communities

More Information about Benthic Communities:

Benthic organisms are important because they are the primary consumers for many ecosystems and are common prey items for many fish and crustacean species. Benthic organisms are also considered to be excellent indicators of environmental stress because Ampipod Crustacean many are sessile and cannot easily avoid exposure to natural or anthropogenic stresses. Characterizing the benthic community in South Carolina coastal habitats is, therefore, essential to the SCECAP program.

More than 43,800 benthic organisms representing 403 taxa were collected from the stations sampled in 1999 and 2000. Species comprising greater than 85% of all organisms collected are listed in Appendix 4.1. Mean abundance of benthic organisms ranged from 6 to 1076 individuals per site (150 to 26,888 individuals/m²), with a greater mean abundance observed at open water stations (5,825 individuals/m²) compared to tidal creek stations (3,575 individuals/m²). This difference was not statistically significant (p = 0.19). Similarly, the mean number of species and Shannon Weiner’s index of overall community diversity (H’) were also higher at open water stations (24 taxa, H’ = 3.05) compared to the tidal creeks stations (17 taxa, H’ = 2.73; Figure 1 below). The statistical difference in mean number of taxa was p = 0.08.

Figure 1. Mean abundance, number of species, and Shannon-Weiner estimate of community diversity (H' ) of benthic fauna in bottom grabs (0.04 m²) collected in open water and tidal creek habitats during 1999-2000.

A list of the 50 numerically dominant taxa is provided in Table 1 below. The five most abundant taxa collected from tidal creeks comprised more than 46% of all animals collected from that habitat type. These included the polychaete worms Streblospio benedicti, Scoletoma tenuis, Polydora cornuta, the amphipod Ampelisca abdita, and the oligochaete Tubificoides wasselli. The five most abundant taxa at open water stations comprised only about 31% of the total fauna from that habitat. These included the polychaetes Streblospio benedicti, Exogone sp., Caulleriella sp., the amphipod Ampelisca abdita, and sea anemones of the order Actinaria. Although Actinaria were dominant in open water stations, 90% of these organisms were collected at one station. Therefore, this taxa is not a good representative of the overall benthic community. The polycheate Caulleriella sp. and the oligochaete Tubificoides wasselli occurred in only about 30% of stations sampled. Conversely, Streblospio benedicti was a numerically dominant organism, especially in creeks, and was present at more than 70% of both open water and tidal creek stations.

Table 1. Abundance and percent of occurrence of the 50 most abundant benthic organisms collected in 1999 and 2000. A =amphipods, M =mollusks, O =other taxa, P =polychaetes. Mean abundance values represent number / 0.04m².

			Open Water		Tidal Creek
Species Name		Total Abundance	Mean Abundance by Station	Percent of Stations	Mean Abundance by Station	Percent of Stations
Streblospio benedicti	P	5831	38	73	63	86
Ampelisca abdita	A	2649	24	53	22	44
Actiniaria	O	2091	34	39	2	26
Scoletoma tenuis	P	1856	13	51	19	72
Caulleriella sp.	P	1817	27	34	4	19
Tubificoides wasselli	O	1680	15	42	14	32
Exogone sp.	P	1671	26	46	3	25
Mediomastus sp.	P	1625	19	59	9	67
Polydora cornuta	P	1128	5	32	14	49
Tharyx acutus	P	1116	10	54	9	54
Mediomastus ambiseta	P	1040	9	53	9	49
Scoloplos rubra	P	972	11	39	5	60
Monticellina sp.	P	947	15	37	1	12
Tubificidae	O	884	11	34	4	49
Tubificoides brownae	O	736	4	51	9	70
Protohaustorius deichmannae	A	715	12	14	0	2
Cirratulidae	P	641	5	47	6	58
Tubificidae sp. b	O	627	10	32	1	16
Heteromastus filiformis	P	500	2	44	6	61
Parapionosyllis sp.	P	473	7	27	1	5
Aricidea wassi	P	466	4	36	4	9
Spiochaetopterus costarum oculatus	P	430	4	27	4	46
Carinomella lactea	O	393	4	44	3	42
Tubificidae sp. a	O	364	6	3	0	4
Cirrophorus sp.	P	355	4	46	2	23
Streptosyllis sp.	P	344	5	32	1	19
Nemertinea	O	343	3	76	2	67
Cyathura burbancki	O	340	5	36	1	11
Nereis succinea	P	328	3	41	3	47
Tellina agilis	M	320	3	29	2	18
Sabellaria vulgaris	P	309	5	25	0	7
Rhepoxynius hudsoni	A	298	3	14	2	7
Pelecypoda	M	288	3	56	2	46
Paraprionospio pinnata	P	284	3	20	2	44
Tubificoides heterochaetus	O	244	2	14	2	7
Unciola serrata	A	242	4	14	0	2
Tellinidae	M	235	2	32	2	25
Mediomastus californiensis	P	231	3	34	1	26
Prionospio sp.	P	226	3	25	1	12
Glycera americana	P	196	2	53	1	60
Phoronida	O	194	1	22	3	25
Turbonilla sp.	M	192	3	10	0	2
Ilyanassa obsoleta	M	188	1	5	3	19
Pinnixa sp.	O	186	3	34	0	25
Lepidactylus dytiscus	A	175	2	5	1	4
Clymenella torquata	P	172	3	20	0	2
Chiridotea stenops	O	168	3	7	0	2
Corophium simile	A	152	2	14	1