EPA - National Lakes Assessment - Zooplankton - 2007

Study Extent

Initial discussion by states and EPA regarding the scope of the survey focused on the size of lakes that were to be considered in the target population. It was agreed that, to be included, the site had to be a natural or man-made freshwater lake, pond or reservoir, greater than 10 acres (4 hectares), at least 3.3 feet (1 meter) deep, and with a minimum of a quarter acre (0.1 hectare) open water. The Great Lakes and the Great Salt Lake were not included in the survey, nor were commercial treatment and/or disposal ponds, brackish lakes, or ephemeral lakes. After applying the criteria, 68,223 waterbodies were considered lakes by the NLA definition and thus comprised the target population.

Sampling

In preparation for the survey, each target lake was screened to verify that it met the established criteria for inclusion in the survey. Throughout the summer of 2007, 86 field crews, consisting of 2 to 4 people each, sampled lakes from Maine to California. At each lake site, crews collected samples at a single station located at the deepest point in the lake and at ten stations around the lake perimeter (Figure 4). At the midlake station, depth profiles for temperature, pH, and dissolved oxygen were taken with a calibrated water quality probe meter or multi-probe sonde. A Secchi disk was used to measure water clarity and depth at which light penetrates the lake (the euphotic zone). NLA analysts used these vertical profile measurements to determine the extent of stratification and the availability of the appropriate temperature regime and level of available oxygen necessary to support aquatic life. Single grab water samples were collected to measure nutrients, chlorophyll-a, phytoplankton, and the algal toxin microcystin. Zooplankton samples were collected using a fine mesh (80µm) and course mesh (243µm) conical plankton net. A sediment core was taken to provide data on sediment diatoms and mercury levels. The top and bottom layers of the sediment core were analyzed to detect possible changes in diatom assemblages over a period of time.

Quality Control

To ensure consistency in data collection and quality assurance, the crews attended a three-day training session, used standardized field methods and data forms, and followed strict quality control protocols including field audits.

Method steps

1. Since a census of every lake in the country is cost prohibitive and beyond the reach of any program, EPA used a statistical sampling approach incorporating state-ofthe-art survey design techniques. The first step, to ascertain the number of lakes in the country, was challenging because there is no comprehensive list or source for all lakes in the U.S. The best resource available is the USGS/EPA National Hydrography Dataset or NHD.

127 different taxa of zooplankton: Acari Chaoborus Keratella
##[4] Bosmina Chaoborus punctipennis Cyclopidae
##[7] Diaptomidae Lecanidae Lepadella
##[10] Ploesoma Polyarthra Synchaeta
##[13] Trichocerca Diaphanosoma Daphnia ambigua
##[16] Temoridae Anuraeopsis Brachionus angularis
##[19] Conochilidae Hexarthra Kellicottia bostoniensis
##[22] Keratella taurocephala Platyias Pompholyx
##[25] Notommata Asplanchna Brachionus caudatus
##[28] Brachionus havanaensis Filinia Gastropus
##[31] None present Ceriodaphnia Chydoridae
##[34] Chironomidae Daphnia mendotae Kellicottia longispina
##[37] Daphnia Polyphemus Daphnia catawba
##[40] Sida Calanoida Chaoborus flavicans
##[43] Holopedium gibberum Collotheca Rotifera
##[46] Daphnia parvula Keratella hiemalis Leptodora
##[49] Moina Euchlanis Daphnia retrocurva
##[52] Eubosmina Dreissena bugensis Dreissena polymorpha
##[55] Testudinella Ergasilus Bdelloidea
##[58] Mytilina Brachionus calyciflorus Brachionus quadridentatus ##[61] Brachionus forficula Keratella testudo Hesperodiaptomus
##[64] Brachionus urceolaris Keratella quadrata Notholca
##[67] Daphnia lumholtzi Tylotrocha Chaoborus albipes
##[70] Centropagidae Cercopagis Unionicola
##[73] Holopedium amazonicum Brachionus bidentata Ascomorpha
##[76] Daphnia laevis Collothecidae Daphnia longiremis
##[79] Aglaodiaptomus Encentrum Colurella
##[82] Ceratopogonidae Brachionus Ptygura
##[85] Brachionus satanicus Brachionus budapestinensis Harpacticoida
##[88] Trichotria Keratella chussa Scapholeberis
##[91] Mysis relicta Wolga Chaoborus americanus
##[94] Lophocharis Simocephalus Proales
##[97] Kellicottia Keratella serrulata Copepoda
##[100] Latona Sinantherina Daphnia ctenodaphnia
##[103] Macrothricidae Brachionus zahniseri Cephalodella
##[106] Epiphanidae Monommata Epiphanes
##[109] Keratella ticinensis Keratella irregularis Daphnia dubia
##[112] Dreissena Brachionus leydigi Keratella valga
##[115] Limnias Wierzejskiella Artemia
##[118] Gammaridae Notommatidae Bythotrephes
##[121] Eurycercus Brachionus pterodinoides Brachionus falcatus
##[124] Resticula Bosminidae Coliothecidae
##[127] Bosminopsis

1. animalia
   common name: Animals rank: kingdom

geographic scope = 48.97903 to 26.93623 latitude; -67.6993 to -124.6325 longitude