Medina River Survey, Texas, 1986: Impact Assessment of 1985 Sulfuric Acid Spill

--- Page 1 --- In September 1985 a train derailment caused several thousand gallons of sulfuric acid to be spilled into the Medina River in southwest Bexar county, Texas. The acid spill and the application of lime (to neutralize the acid) negatively impacted approximately 29 miles of river below the spill site. In order to determine the degree of rejuvenation that has occured, electrofishing, seine and benthic samples were collected from six sites along the Medina River, Figure l. Data from the sample sites above the spill (1-3) was compared to data from the derailment site and the two downstream stations (4-6). The sites above the spill had a higher species diversity and significant differences were found in the mean number of species from both electro- fishing and seine samples (Tables 1-2). A significant difference was also found in the mean number of fish from electrofishing data. Species diversity of benthic organisms was somewhat higher at sites above the spill site but no significant differences were found for mean number of organisms or families (Table 3-4). It appears the benthic organisms are recovering more rapidly than the fish population w --- Page 2 --- 1604 Pearsall Road (2536) = es #1 ) Le os5 Southern Pacific Medina River #5 #6 Figure 1. Sampling sites on the Medina River, Texas, February 2-4, 1986. --- Page 3 --- Table 1 . Electrofishing statistics, six stations, Medina River Texas, January-February 1986. Above Spill Spill Below Spill Stations 1 2 3 4 5 6 Species Mexican tetra - ~ = 1 1 = Speckled chub - 1 2 - = _ Blacktail shiner 1 3 - = = uf Red shiner - 2 a = = = Sand shiner _ 1 = = = ah Stoneroller 16 7 3 = = al Channel catfish _ = 1 a = a Tadpole madtom - - 1 a = = Blackstriped topminnow - 1 - - on = Gambusia 1 7 2 1 1 1 Sailfin molly 9 10 29 12 2 - Spotted bass 1 4 1 = = = Warmouth ~ - 1 = “eo = Green sunfish - 13 11 = 5 = Spotted sunfish 3 - - a os a Bluegill 2 13 1 4 = 1 Redbreast sunfish 3 2 - = - mI Longear sunfish - 4 6 Pa z a Logperch 2 1 - 1 1 - Rio Grande cichlid 1 3 1 4 - =“ Total 40 74 62 27 15 2 Number species 10 15 12 6 5 2 --- Page 4 --- Table 2. Seine sampling statistics, six stations, Medina River, Texas, January 1986. Stations Above Spill Spill Site Below Spill 1 2 3 4 5 6 eee Species Mexican tetra - - - - - 2 Speckled chub 1 1 = 5 at “ Blacktail 10 7 32 i a - shiner Red shiner - - 14 - - 5 Bullhead minnow - 1 4 = - - Largemouth bass - - = l = = Bluegill sunfish - 1 - si = # Longear sunfish 3 1 - = - = Tadpoles - - l - ae 1 Crawfish - = - = as 1 --- Page 5 --- Table 3. Benthic sampling statistics collected with a surber sampler from six sites on the Medina River, Texas, January-February, 1986. Sites Family Tendipedidae Baetidae Hydropsychidae Coenagrionidae Daphnia Ecdyuriidae Potamanthidae Libellulidae Psephenidae Simuliidae Dixidae Siphlonuridae Tipulidae Naucoridae Physidae Sphaeriidae Ephemeridae Elmidae Hydroptilidae 16 10 39 18 17 Total number Number Families 145 13 Above Spill Spill Site Below Spill 2 3 4 5 6 32 5 Zl 16 30 13 23 99 6 2 1 9 42 1 we a = 1 1; - 1 = = 1. 2 1 10 1 2 13 3 22 1 - 1 - - - 1 - * as 1 == - - 1 50 4 = 2 - “ - = 3 a a - 28 = i on 9 - 1 a x = = 1 ne - - = 2 es 2 4 4 om we - 1 - 2 4 8 3 2 = co 73 25 125 223 18 8 11 11 13 7 --- Page 6 --- Table 4 . Benthic sampling statistics collected with an Ekmann Dredge ( total number organisms ) from six sites on the Medina River, Texas, January- February, 1986. -__ SK Above Spill Spill Site Below Spill Sites 1 2 3 4 5 6 Total Number 240 55 156 518 299 28 --- Page 7 --- Species Diversity Analysis - Medina River Electrofishing Results Species Above Spill Site At or Below Spill Site Ce enn nee eee eee, eee Channel catfish Blacktail shiner Tadpole madtom Gambusia spp. Mexican tetra Logperch Sailfin molly Stone roller Bluegill Spotted sunfish Redbreast sunfish Spotted bass Rio Grande cichlid Longear Green sunfish Warmouth Red shiner Speckled chub Sand shiner Blackstriped topminnow te a ee eee eee Number of species Species Diversity (Shannon index) eee eee a ee ee eee Mean number of fish Mean number of species Site 1 Site 2 1 3 1 7 2 1 9 10 16 7 2 13 3 3 2 1] 4 1 3 4 13 2 ] 1 ] 39 72 10 15 0.77 1.03 Above Spill Site 56.67 12.33 Site 3 Site 4 1 1 2 1 1 ] 29 12 3 1 4 1 1 4 6 11 1 2 59 23 12 6 0.73 0.59 At or Below Spill Site 11.67 4.33 0.30 t Test * calculated 3.96 sign. 4.23 sign. There are statistically significantly more fish and numbers of fish species above the spill site than at or below the spill site. Species diversity is also consic- kk kk --- Page 8 --- Species Diversity Analysis - Medina River Seining Results Above Spill Site At or Below Spill Site SPecfes Shih ec cere een eerneee esewenmctenneemetncencees Totals Renn onnnncaseaecancecea <a Mexican tetra 2 2 Speckled chub 1 1 5 7 Blacktail shiner 10 7 32 49 Red Shiner 4 14 5 23 Bullhead minnow 1 4 5 Largemouth bass 1 1 Bluegill 1 1 Longear 3 1 Totals 18 11 50 6 0 7 92 Number of species 4 5 3 2 0 2 8 Species Diversity 0.49 0.50 0.37 0.20 0.00 0.26 0.59 (Shannon index) Statistics eesesseS At or t Test * Above Below Spill Spill calculated Site Site t Mean number of fish 26.33 4.33 1.80 not sign. Mean number of species 4.00 1,33 3.03 sign. * Co ieeieeieietet tet) There are statistically significantly more species of fish above the spill site than at or below, but there is no significant difference in number of fish. This is due to wide vari- ations in number of fish taken in seine hauls across all sites. Species diversity is much greater at the above spill sites. --- Page 9 --- Surber Results Species Diversity Analysis - Medina River Surber and Eckman Sampling Results Above Spill Site At or Below Spill Site «tape Taxd nee nee nneneeeeeeeeeee eee Totals Site 1 Site 2 Site 3 Site 4 Site 5 Site 6 : Tendipedidae 16 32 5 21 16 30 120 Baetidae 10 13 2 23 99 6 153 Hydropsychidae 4 2 1 9 42 1 59 Coenagrionidae 1 1 3 Daphnia spp. 1 1 . Ecdyurtidae 3 2 1 10 1 2 19 , P Zotamanthidae 22 13 3 22 1 61 Libellulidae 1 1 2 Psephenidae 6 ] 7 Simuliidae 1 ] 50 4 56 Dixidae 2 2 Siphlonuridae 3 3 6 Tipulidae 3 28 31 Nawcoridae 2 ] 3 pthysidae 3 1 4 SphaerJdiidae 3 2 5 Ephemeridae 39 2 4 é 49 Fe Elmidae 18 1 2 4 25 vs Hydroptilidae 17 8 3 2 30 * 0 & oh Totals 145 73 25 125 220 48 636 i Number of taxa 13 8 11 11 13 7 19 & ay Taxon Diversity 0.94 0.68 0.98 0.87 0.65 0.55 4.09 B (Shannon index) y Eckman Results Individuals Total 240 55 156 518 299 28 were eeen-- ; At or t Test * Statistics Above Below wer teneeen- Spill Spill calculated Site Site t ** Surber ** Mean number of individuals 81.00 131.00 -823 not sign. Mean number of taxa 10.67 12.33 -118 not sign. ** Eckman ** Mean number of individuals 150.33 281.67 -708 not sign. * for df = 4, alpha = 0.05, two-tailed test, critical t = 2.776 --- Page 10 --- Heart of the Hills Research Station Texas Parks and Wildlife Department Junction Star Route 62 Ingram, TX 78025 February 7, 1986 Texas Parks and Wildlife Department 4200 Smith School Road Austin TX 78744 ATTN: Phil Durocher, Inland Fisheries PPS Dear Phil: Enclosed is a second set of data and analysis from benthos data collected by Jimmy Dean. Note that only a single table presents results from both Surber and Eckman dredge samples. Only total number of individuals is reported for each station for Eckman samples. These results indicate that there is no Significant difference in number of individuals or number of taxa between the above spill sites and the "at or below spill" sites. The diversity index indicates that there is somewhat more diversity at the "above" sites, but this is largely due to more "evenness" in the spread of individuals among the taxa present at each site. Note also that the particular taxa present differ between the above and below sites; since we do not have species identifications, it would be difficult to comment on the relative sensitivities, hardiness, or re-establishment capabilities of these taxa. , I hope that these results will be of use to you in the Medina River assessments. Let me know if I can be of further assistance. Sincerely, Navhad Clete Michael Childress wmc --- Page 11 --- Species Diversity Analysis - Medina River Surber and Eckman Sampling Results Surber Results Above Spill Site At or Below Spill Site Taxa wenn nnn enna nnn nn nnn ne ee Hoenn eee ee eee Totals Tendipedidae 16 32 5 21 16 30 120 Baetidae 10 13 2 23 99 6 153 Hudropsychidae 4 2 1 9 42 1 59 Coenagrionidae 1 1 Daphnia spp. 1 1 Ecdyuriidae 3 2 1 10 1 2 19 Totamanthidae 22 13 3 22 1 61 Libellulidae 1 1 2 Psephenidae 6 ] 7 Simuliidae 1 1 50 - 56 Dixidae 2 2 4 Siphlonuridae 3 3 Tipulidae 3 28 31 Navcoridae 2 1 3 Thysidae 3 1 4 Sphaeridiidae a zZ 5 Ephemeridae 39 2 4 4 49 Elmidae 18 1 2 4 25 Hydroptilidae 17 8 3 2 30 0 Totals 145 73 25 125 220 48 636 Number of taxa 13 8 11 ll 13 7 19 Taxon Diversity 0.94 0.68 0.98 0.87 0.65 0.55 1.00 (Shannon index) Eckman Results Individuals Total 240 55 156 518 299 28 aie At or t Test * Statistics ; Above Below ---------- Spill Spill calculated Site Site t ** Surber ** Mean number of individuals 81.00 131.00 -823 not sign. Mean number of taxa 10.67 12.33 .118 not sign. ** Eckman ** Mean number of individuals 150.33 281.67 -708 not sign. * For df = 4, alpha = 0.05, two-tailed test, critical t = 2.776