State of the Lake 2009 - Tahoe Environmental Research Center ...

Recommendations

Info

ASIAN CLAM Asian Clam in Lake Tahoe In spring 2008 UC Davis researchers discovered extensive and often dense beds of an invasive bivalve, the Asian clam (Corbicula fluminea) in southeastern Lake Tahoe in nearshore Asian clams are relatively small in size, ranging from 1 mm to 55 mm in most systems. In Lake Tahoe, the largest clam only gets to be about 30 mm in size, likely due to colder water temperatures and low calcium and food (algal) availability in the lake. TAHOE: STATE OF THE LAKE REPORT 2009 areas from Zephyr Cove to El Dorado Beach. Observations by researchers at the University of Nevada Reno of small numbers of clams (densities of 3-20 individuals per square meter) Asian clams live within the sandy bottom of lakes. They can burrow into the sediments using a strong muscle called a “foot”. Ridges on their shells help them burrow into sediments and stay anchored in the bottom when water currents move across them. Asian clam are capable of both filter feeding and pedal (foot) feeding—drawing from both the water column and the bottom sediments for nutrition. One reason for the Asian clam’s success in a wide range of habitats is that it can effectively filter phytoplankton and bacteria out of the water column and deposit feed when pelagic (lake water) food becomes scarce. in 2002 suggest that Asian clam may have been in Lake Tahoe for at least 6 years; however, the densities and size of the recently observed beds are much larger than previously reported. Researchers are currently studying the impacts of the clams to Lake Tahoe. By measuring sediment porewaters (the water between sediment grains on the bottom of the lake) scientists can understand how Asian clam are contributing to the amount of nutrients in the lake bottom, including the deposition of calcium through degrading clam shell matter. These accumulations of high calcium regions may facilitate the invasion of other calcium loving species, such as the quagga or zebra mussel. TERC.UCDAVIS.EDU 6.2
100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% ASIAN CLAM Invertebrate Composition In addition to Asian clams, there are a number of other native benthic invertebrates that live in the sandy bottom of Lake Tahoe. This includes a native pea clam which can get up to 4 mm in length, only ~1/8 as large as the Asian N = 1381 N = 354 106 259 337 635 19 24 Marla Bay Zephyr Cove Fall 2008 52 66 194 38 TAHOE: STATE OF THE LAKE REPORT 2009 clam adult. There are also many other snail, worm, and crustacean species that live in the bottom where Asian clam are found. Researchers are currently studying the impacts of Asian clam on other invertebrate species, 1 3 Pisidium spp. (native pea clams) Gastropoda (snails) Amphipoda (shrimp−like crustaceans) Diptera (fly larvae) Oligochaeta (worms) Corbicula fluminea (Asian clams) TERC.UCDAVIS.EDU 6.3 Other such as the possible decrease of benthic biodiversity as a result of Asian clam. In areas where Asian clam densities are high, it has been observed that native pea clam densities are relatively lower.
Page 1 and 2: TAHOE: STATE OF THE LAKE REPORT 200
Page 3 and 4: INTRODUCTION The University of Cali
Page 5 and 6: EXECUTIVE SUMMARY (CONTINUED FROM P
Page 7 and 8: ABOUT LAKE TAHOE AND THE TAHOE BASI
Page 9 and 10: MAP OF TAHOE BASIN DATA COLLECTION
Page 11: Rainbow, Brook, Brown and Lake trou
Page 15 and 16: ASIAN CLAM Asian Clam Excretion Exp
Page 17 and 18: ASIAN CLAM Asian Clam Size Distribu
Page 19 and 20: Temperature ( o F) 60 55 50 35 30 M
Page 21 and 22: Temperature ( o F) 70 60 50 40 30 2
Page 23 and 24: Inches 70 60 50 40 30 20 10 0 METEO
Page 25 and 26: Percent 80 70 60 50 40 30 20 10 0 M
Page 27 and 28: PHYSICAL PROPERTIES TERC.UCDAVIS.ED
Page 29 and 30: Feet 6232 6230 6228 6226 6224 6222
Page 31 and 32: Temperature ( o F) TERC.UCDAVIS.EDU
Page 33 and 34: Temperature ( o F) TERC.UCDAVIS.EDU
Page 35 and 36: Density Difference (kilograms per c
Page 37 and 38: Mean daily streamflow (cubic feet p
Page 39 and 40: NUTRIENTS AND PARTICLES TERC.UCDAVI
Page 41 and 42: TERC.UCDAVIS.EDU NUTRIENTS AND PART
Page 43 and 44: Metric Tons TERC.UCDAVIS.EDU 10 8 6
Page 45 and 46: Dissolved inorganic nitrogen (micro
Page 47 and 48: Nitrate−nitrogen (micrograms per
Page 49 and 50: BIOLOGY 10
Page 51 and 52: BIOLOGY Algae abundance Yearly sinc
Page 53 and 54: BIOLOGY Depth of chlorophyll maximu
Page 55 and 56: BIOLOGY TAHOE: STATE OF THE LAKE RE
Page 57 and 58: BIOLOGY Nutrient limitation of alga
Page 59 and 60: BIOLOGY Shoreline algae distributio
Page 61 and 62: TERC.UCDAVIS.EDU CLARITY Annual ave
Page 63 and 64:
Depth (feet) TERC.UCDAVIS.EDU CLARI
Page 65:
TERC.UCDAVIS.EDU OUTREACH AND EDUCA
show all

State of the Lake 2009 - Tahoe Environmental Research Center ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?