Effect of methodology and sampling time on the taxa richness of
Contents
1. The most diverse group was Coleoptera with 18 genera most of which belong to the family of Elmidae A total of 3 214 individuals were collected in the three rivers and the most abun dant order was Ephemeroptera which made up 42 4 of the total number of individuals The abundance didn t necessarily increase with an increasing sampling time in the first method Figs 1A C In some cases R o Uvita R o San Lorencito more than twice the number of individuals was found in 3 minutes than in 5 or 10 minutes With one exception R o Balso rainy season a TABLE 2 Aquatic macroinvertebrates collected in R o Uvita R o Balso and R o San Lorencito in both seasons with both methods Taxa Ephemeroptera Baetidae Americabaetis sp Baetidae Baetodes sp Baetidae Camelobaetidius sp Baetidae Cloeodes sp Baetidae Gen sp Baetidae Mayobaetis sp Baetidae Moribaetis sp Euthyplociidae Euthyplocia sp Leptohyphidae Haplohyphes sp Leptohyphidae Leptohyphes sp Leptohyphidae Tricorythodes sp Leptohyphidae Vacuperinus sp Leptophlebiidae Farrodes sp R o Uvita R o Balso R o San Lorencito X X X X X X X X X X X X X X X X X X X X X X X X X X 260 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 TABLE 2 Continued Aquatic macroinvertebrates collected in Rio Uvita Rio Balso and Rio San Lorencito in both seasons with both methods Taxa Rio Uvita Rio B2. 3 5 40 20 4 Genera a Family 8 10 Acumulative nr of minutes 40 Accumulative nr of taxa 0 3 5 C E d 4 Genera 30 m Family 5 20 a 8 10 Acumulative nr of minutes Fig 3 Accumulative number of genera and families collected with the first method in the rainy season in the three rivers a Rio Uvita b Rio Balso c Rio San Lorencito minutes of collection Figs 3A C and Figs 5A C independent of season or river Species accumulation curves for samples taken during 120 minutes with the second method show that new genera and families were still found after 120 minutes Figs 4A C and Figs 6A C One exception is the Rio San Lorencito in the dry season After 90 minutes no new genera and families were found Fig 6C BMWP CR index In general categories of water quality obtained from the BMWP CR index varied greatly among sampling times and methods used With the second method the BMWP CR index of all three rivers was always higher than with the first method Figs 7A B The greatest difference was in the R o Uvita in the dry season which stayed in the yellow level contaminated bad water quality with the first method but reached the blue level good water quality with no obvious contamination with the second method Fig 7B In the rainy season the situation was similar although not as evident Fig 7A The BMWP CR index repr
3. 1978 Recently efforts have been undertaken to adapt this index to the Costa Rican fauna BMWP CR index in order to include it in the new Costa Rican water law as an official measurement for biomonitoring 1 During the process of publication the methodology for aquatic biomonitoring using the BMWP CR index was published in the regulation Nr 33903 MINAE S La Gaceta No 178 17 Sept 2007 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 259 TABLE 1 Categories of water quality defined by the BMWP values according to Alba Tercedor 1996 Water quality waters with excellent quality waters with good quality no contaminations or obvious distortions waters with regular quality eutrophic medium contamination waters with bad quality contaminated waters with bad quality very contaminated waters with very bad quality extremely contaminated The levels of water quality are defined by the BMWP index as in Table 1 These levels are obtained by adding the sensitivity value from 1 10 for each family found independently of the abundance and generic diversity found in each family RESULTS Abundance and taxa richness For all sampling sites a total of 89 genera were found representing 40 insect families nine insect orders and five non insect classes Table 2 BMWP associated color gt 120 blue 101 120 blue 61 100 green 36 60 yellow 16 35 orange lt 15 red
4. 2B C 35 A Method 1 Genera Species accumulation curve The accu mulative number of genera and the accumula tive number of families was usually higher in the dry season than in the rainy season no matter what method was used Figs 3 6 Exceptions are the Rio Balso where more genera and families were found with the first method in the rainy season Fig 3B and the Rio San Lorencito where one additional genus was found in the rainy season Fig 4C than in the dry season with the second method Fig 6C Species accumulation curves for samples taken with the first method show that new genera and families were still found after 10 Method 2 E Rainy season O Dry season y 5 8 Collecting time 10 B Method 1 30 20 Genera 10 60 120 Method 2 E Rainy season O Dry season 3 5 8 Collecting time 30 Method 1 Genera N o 10 60 120 Method 2 W Rainy season E Dry season 3 a 8 Collecting time Fig 2 Total number of genera of aquatic macroinvertebrates collected in three rivers with both methods in both seasons a Rio Uvita b Rio Balso c Rio San Lorencito 264 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 Accumulative nr of taxa 3 5 4 Genera a Family 8 10 Acumulative nr of minutes 60 B Accumulative nr of taxa
5. 40 iC Accumulative nr of taxa 15 30 45 60 30 i pm 10 a Family 90 105 120 Acumulative nr of minutes Fig 6 Accumulative number of genera and families collected with the second method in the dry season in the three rivers a Rio Uvita b Rio Balso c Rio San Lorencito combined shows that a still higher ranking is possible which could also be seen with the species accumulation curves Since the highest number of collected families reflects the real water quality of the river neither of the two methods used in this study fulfills the expecta tions Comparing the two methods the second method always achieves a higher level than the first method and therefore could be con sidered to be the more representative one On the other hand both methods showed different results in the rainy and the dry season In the dry season the BMWP CR index seems to be higher than in the rainy season and therefore it might make sense to adapt the index or the methodology to each season Also it has to be considered that Costa Rica is a very hetero geneous country with significant differences 268 in precipitation depending on elevation and location Atlantic versus Pacific slopes and Central Valley and therefore it might be practical to adapt the BMWP CR index for the different provinces or watersheds Concerning the expenditure of human labor the first method is more time consuming since
6. and grit and there was hardly any dead wood water tem perature was 27 C in the rainy and 30 C in the dry season The Rio Balso lies in the same region as the Rio Uvita and samples were taken 12 km north of the settlement of Ojochal and about 20 km before the mouth of the river into the Pacific 09 03 N 83 09 W 180 m a s l The study site is surrounded by primary rain forest without any anthropogenic influence at this point or in the upstream area Climate data are the same as for the Rio Uvita The samples were taken on the 30 of Nov 2003 and on the 18 of Feb 2004 The average width of the Rio Balso changed from 2 m to 50 cm and the depth from 20 cm to 10 cm The substrate 258 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 consisted of stones grit and organic matter in the form of dead wood and leafpacks in decom position the water temperature was 21 C for both sampling dates The Rio San Lorencito is located in Alajuela province in the northern highlands of Costa Rica The climate is classified as asea sonal hyper humid with annual precipitation over 4000 mm and an average annual tempera ture of 21 C In general the wet season is from June until September 800 mm month and the dry season from February to May 150 mm month The Rio San Lorencito is a branch of the Rio San Lorenzo and lies in the Cordillera de Tilaran The samples were taken 100m upstr
7. se utiliza oficialmente en muchos proto colos de biomonitoreo en zonas templadas estos resultados sugieren que a n es necesario realizar m s estudios sobre el tiempo de recolecta y la metodolog a m s adecuada para r os tropicales Palabras clave biomonitoreo macroinvertebrados acu ticos calidad del agua curva de acumulaci n de especies ecolog a de r os Costa Rica REFERENCES Alba Tercedor J amp A Sanchez Ortega 1988 Un m todo r pido y simple para evaluar la calidad biol gica de las aguas corrientes basada en el de Hellawell 1978 Limn tica 4 51 56 Alba Tercedor J 1996 Macroinvertebrados acu ticos y calidad de las aguas de los r os IV Simposio del Agua en Andaluc a SIAGA Almeria 203 213 Charpentier C amp F A Tabash 1988 Variaciones en la diversidad de la comunidad bent nica del sedimento Un indicador biol gico del estado de contaminaci n de los r os de la subregi n de Heredia Costa Rica Uniciencia 5 69 76 Diaz Martinez J A 1995 Efecto del nivel de resoluci n tax on mico sobre la determinaci n de bioindicadores en estudios de impacto ambiental Sociedad Colombiana de Entomolog a Santa Fe de Bogot Colombia Fenoglio S G Badino F Bona 2002 Benthic mac roinvertebrate communities as indicators of river environment quality an experience in Nicaragua Rev Biol Trop 50 1125 1132 Flowers R W amp C M Pringle 1992 Yearly fluctuations in the may
8. why more genera were generally found with the second method because here a much longer distance along the river was covered during the Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 w o gt Accumulative nr oftaxa N o o o 3 5 Genera a Family 8 10 Acumulative nr of minutes 40 Accumulative nr of taxa 10 3 5 J MM c Ps Qu aes Genera m Family 8 10 Acumulative nr of minutes 50 C 40 30 Accumulative nr of taxa 3 5 4 Genera a Family 20 a a aac 8 10 Acumulative nr of minutes Fig 5 Accumulative number of genera and families collected with the first method in the dry season in the three rivers a Rio Uvita b Rio Balso c Rio San Lorencito 2 h collecting time There is also a difference between leaf packs since fresh leaves don t house as many aquatic macroinvertebrates as older accumulations With the second method one realizes very quickly whether an accumu lation houses many individuals or not If only a few individuals are found one has the option of discarding the sample and going on to the next microhabitat while with the first method a less rich microhabitat is noticed only in the laboratory The generally higher abundance and taxa richness with the second method shows that a higher sampling effort
9. y los macroinvertebrados fueron separados posteriormente en el laboratorio Con la segunda metodolog a los orga nismos fueron recolectados directamente desde el colador por un tiempo total de recolecta y separaci n de 120min y preservados en el campo en alcohol al 70 Con el fin de obtener curvas de acumulaci n de especies para este m to do se tomaron submuestras cada 15min El an lisis de los resultados mostr que tanto la abundancia como la riqueza taxon mica fueron mayores con el segundo m todo de recolecta directa y una mayor cantidad de g neros pudo ser encontrada con un mayor tiempo de recolecta aunque no necesariamente una mayor cantidad de individuos Entre poca lluviosa y poca seca se observ una diferencia en el n mero de individuos Las curvas acumulativas de especies para las muestras tomadas con ambas metodolog as mos traron que a n despu s del m ximo tiempo de recolecta se encontraron nuevos g neros y familias independientemen te de la poca o del r o Las categor as de calidad de agua obtenidas del ndice BMWP CR var an fuertemente entre tiempos de recolecta y m todo utilizado El segundo m to do de recolecta directa siempre revel una mejor calidad de agua que el mayor tiempo de recolecta indirecta 10min del primer m todo Sin embargo tampoco lleg al nivel que se obtuvo si se sumaron todas las familias encontradas con ambas metodolog as combinadas Aunque el primer m todo es el que
10. Effect of methodology and sampling time on the taxa richness of aquatic macroinvertebrates and subsequent changes in the water quality index from three tropical rivers Costa Rica Thomas Maue amp Monika Springer 3 1 2 3 Hydrobiologie Universitat Essen Duisburg Essen Germany tmaue web de Escuela de Biolog a Universidad de Costa Rica 2060 San Jos Costa Rica springer biologia ucr ac cr Centro de Investigaci n en Ciencias del Mar y Limnolog a CIMAR Universidad de Costa Rica 2060 San Pedro de Montes de Oca Costa Rica Received 02 111 2005 Corrected 05 V 2008 Accepted 03 VI 2008 Abstract Aquatic macroinvertebrates have proven to be a useful tool for water quality studies and biomonitor ing in temperate areas Recently efforts have been made to adapt these methods to tropical environments but there are still uncertainties concerning the most adequate methodology and collecting time Three rivers one in Alajuela province and two in Puntarenas province in Costa Rica were tested with two methods and different collecting times in the rainy and dry season The first method involved collecting of organic and inorganic mate rial for a fixed time period 3 5 8 10 min with a strainer This material was transferred to a plastic bowl con taining 70 alcohol and aquatic macroinvertebrates were sorted out in the laboratory With the second method the specimens were collected in the field directly out of the strainer for a t
11. also Rio San Lorencito Leptophlebiidae Hagenulopsis sp X Leptophlebiidae Thraulodes sp X X X Leptophlebiidae Traverella sp X Plecoptera Perlidae Anacroneuria sp X X X Odonata Calopterygidae Hetaerina sp X X X Coenagrionidae Argia sp X X X Gomphidae Gen sp X Libellulidae Brechmorhoga sp X X Libellulidae Perithemis sp X Megapodagrionidae Gen sp X X Megapodagrionidae Heteragrion sp X Megapodagrionidae Phylogenia sp X Platysticitidae Perigomphus sp X Polythoridae Cora sp X X X Hemiptera Hebridae Hebrus sp X Naucoridae Ambrysus sp X Naucoridae Limnocoris sp X Veliidae Rhagovelia sp X X X Megaloptera Corydalidae Corydalus sp X X X Corydalidae Chloronia sp X Trichoptera Calamoceratidae Phylloicus sp X X Glossosomatidae Culoptila sp X X Glossosomatidae Mexitrichia sp X X Glossosomatidae Protoptila sp X X Hydrobiosidae Atopsyche sp X Hydropsychidae Calosopsyche sp X Hydropsychidae Leptonema sp X X X Hydropsychidae Macronema sp X Hydropsychidae Smicridea sp X X X Hydroptilidae Ochrotrichia sp X Leptoceridae Nectopsyche sp X X X Leptoceridae Oecetis sp X X Philopotamidae Chimarra sp X X X Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 261 TABLE 2 Continued Aquatic macroinvertebrates collected in Rio Uvita Rio Balso and Rio San Lorencito in both seasons with both methods Taxa Polycentropodidae Polyce
12. cu ticos del Departamento de Antioquia Presencia Bogot Colombia Rosenberg D M amp V H Resh 1993 Introduction to Freshwater Biomonitoring and Benthic Macroinvertebrates pp 1 9 In D M Rosenberg amp V H Resh eds Freshwater Biomonitoring and Benthic Macroinvertebrates Chapman amp Hall London Inglaterra Schwoerbel J 1999 Einfuehrung in die Limnologie Gustav Fischer Stuttgart Alemania Springer M 1998 Genera of aquatic insects from Costa Rica deposited at the Museo de Zoologia Universidad de Costa Rica Rev Biol Trop 46 suppl 6 137 141 Stein H M Springer amp B Kohlmann 2008 Comparision of two sampling methods for biomonitoroing using aquatic macroinvertebrates in the Dos Novillos River Costa Rica Pp 267 275 In B Kohlmann amp W J Mitsch eds Ecological management and sustain able development in the humid tropics of Costa Rica Ecol Engineer 34 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 271
13. eam from the research station at the south east border of the Biological Reserve Manuel Brenes 10 13 N 84 37 W 960 m a s l The stream is surrounded by primary forest and there is no antropogenic influence at or above the sampling site Samples were taken on November 11 2003 and on March 13 2004 The average width 5 m and depth 60 cm were the same for both seasons and precipita tion was unusually high for this dry season The substrate consisted of boulders stones gravel sand and organic matter in the form of leaf packs in decomposition a large amount of dead wood was also present The current conditions varied among microhabitats from fast flowing riffles to calm pools water temperature was 18 C for both sampling dates Methods For collection a mesh strainer with a mesh opening of 1mm an inner diameter of 21cm and a depth of 10 cm was used All microhabitats present were sampled on both sides of a river the direction of collection was always upstream With the first method material from the different microhabitats of a river was collected during a predetermined collection time and included organic and inorganic material such as leaves grit and sticks The collection times were 3 min 5 min 8 min and 10 min which means that four independent collections were obtained with the first method at each river The collected material was transferred into a plastic bowl and 70 alcohol was added to preserve
14. esenting all families found in both methods combined was for all three rivers consider ably higher than for each method alone Figs 7A B A correlation between the number of genera and the BMWP CR index was found Pearson lt 0 05 This is due to the fact that with a rising number of genera more families are represented and therefore the BMWP CR index is higher None of the other parameters individuals rivers seasons and sampling time showed any correlation Pearson gt 0 05 to the BMWP CR index DISCUSSION The fact that the number of collected aquat ic macroinvertebrates is not correlated with the Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 265 15 30 45 60 Accumulative nr of taxa So Genera m Family 25 90 105 120 Acumulative nr of minutes 40 B Accumulative nr of taxa nisi 30 45 60 30 20 10 Genera m Family 75 90 105 120 Acumulative nr of minutes 40 30 20 Accumulative nr of taxa 15 30 45 60 4 Genera a Family La 90 105 120 Acumulative nr of minutes Fig 4 Accumulative number of genera and families collected with the second method in the rainy season in the three rivers a Rio Uvita b Rio Balso c Rio San Lorencito sampling time in the first method and in some cases even m
15. fly community of a tropical stream draining lowland pasture in Costa Rica Proc VII Intl Conf Ephemeroptera Hellawell J M 1978 Biological surveillance of rivers Water Research Center Hertfordshire Inglaterra 270 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 Kricher J 1997 A Neotropical Companion Princeton University Princeton Nueva Jersey Mafla Herrera M 2005 Guia para evaluaciones ecol gicas r pidas con indicadores biol gicos en r os de tama o mediano Talamanca Costa Rica Serie t cnica Manual T cnico No 61 CATIE Turrialba Costa Rica 90 p Michels A 1998 Use of diatoms for water quality assess ment in two tropical streams in Costa Rica Rev Biol Trop 46 143 153 Merritt R W amp K W Cummins eds 1996 An Introduction to the Aquatic Insects of North America Kendall Hunt Dubuque lowa EEUU Paaby P 1993 Sondeo acu tico de la zona Atl ntica Norte Situaci n actual antes de la producci n de banano Corporaci n Bananera Nacional Costa Rica Paaby P A Ram rez 8 C M Pringle 1998 The benthic macroinvertebrate community in Caribbean Costa Rican streams and the effect of two sampling meth ods Rev Biol Trop 46 185 199 Rold n P rez G R 1992 Fundamentos de Limnolog a Neotropical Universidad de Antioquia Medell n Colombia Rold n P rez G R 1996 Gu a para el estudio de los macroinvertebrados a
16. formed around the world using aquatic macroinvertebrates as bioindicators in order to monitor the water quality of surface water This group of organ isms is especially useful for biomonitoring due to their relatively sedentary behavior long life spans and nearly similar abundance around the world Schwoerbel 1999 Rosenberg and Resh 1993 In addition collection and identification techniques are inexpensive in comparison to chemical analysis and other methods of water testing Also biomonitoring with macroin vertebrates shows long term changes while chemical analysis can be considered a snap shot and reflects only the momentary water quality situation Alba Tercedor 1996 All together these characteristics make benthic macroinvertebrates especially advantageous for water quality evaluation Since aquatic insects evolved over a similar time period all over the world some authors consider that methods using these organisms as bioindicators are Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 257 also compatible around the world Schwoerbel 1999 The use of aquatic insects as bioindicators had been studied primarily in temperate zones such as Europe and the United States and there is still a lack of knowledge of benthic macro invertebrate ecology and distribution in the neotropics Roldan 1992 which makes such evaluation of the water difficult but neces sary Due to thi
17. ion time and methodology used between the rainy season and dry season Collecting methodology consequently influences the results of the water quality index used and may result in different categories of water quality MATERIAL AND METHODS Study areas Aquatic macroinvertebrates were collected in three rivers in Costa Rica Rio Uvita Rio Balso and Rio San Lorencito Rio Uvita lies in the province Puntarenas in the south western lowlands of Costa Rica The samples for this study were taken 2 km north east of the town Uvita and about 4 5 km before the Rio Uvita ends in the Pacific 09 09 N 83 44 W 10 m above sea level The area sur rounding the study site is pasture land on one side and farmland with shrub vegetation and some eucalyptus trees on the other There is one small settlement San Josecito 6 km upstream from the investigated area In the past poison was used by locals to catch fish and shrimp in the river The climate is classified as aseasonal humid with annual precipitations between 2500 to 3500 mm and an average annual temperature of 26 C The wet season is from May until December 700mm month and the dry season between January and April 50mm month Samples were taken for the rainy season on the 6 of Oct 2003 and during the dry season on the 4 of Feb 2004 The average width of Rio Uvita shrank from 10 m to 3 m and the aver age depth from 90 cm to 40 cm The river bed was mainly covered by stones
18. is required with the first method In order to guarantee a more represen tative sample with the first method it is neces sary to collect a higher number of replicates of the medium time samples 5 or 8 min rather than increasing the sampling time of a single sample More investigation is needed to indi cate the optimal number of replicates required This is also indicated by the species accu mulation curves which showed that new gen era and families were still being found after the maximum collecting time regardless of season or river and therefore more studies are needed to find out when the maximum taxo nomic diversity of aquatic macroinvertebrates will be collected Several authors Paaby 1993 Flowers and Pringle 1992 Wallace cited in Kricher 1997 mention that the large majority of organisms found in the neotropics are in contrast to the temperate zones represented by very few individuals but in a vast diversity The total BMWP CR index calculated by using all families found in both methods Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 267 40 A 4 Genera a Family 90 105 120 Genera a Family 90 105 120 Genera 2 ES 20 3 gs 10 0 15 30 45 60 75 Acumulative nr of minutes 40 e B gg 30 25 Eo 20 gE lt 10 0 15 30 45 60 75 Acumulative nr of minutes
19. la X Crustacea Astacidea X X Crustacea Brachyura X Hidracarina X Molusca Gastropoda X Oligochaeta X X X Tricladida Planariidae X X X A 300 Method 1 Method 2 W Rainy season 250 E1 Dry season 200 3 Me gt 150 o c 100 50 Individuals 3 5 8 10 60 120 Collecting time Method 1 Method 2 W Rainy season E Dry season 100 3 5 8 10 60 1 20 Collecting time E 300 Method 1 Method 2 250 200 150 100 50 E Rainy season E Dry season Individuals 3 5 8 10 60 120 Collecting time Fig 1 Total number of individuals of aquatic macroinvertebrates collected in three rivers with both methods in both season a Rio Uvita b Rio Balso c Rio San Lorencito Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 263 higher abundance was found with the second method Even though the number of individu als didn t generally rise with an increasing sampling time first method there was an obvious tendency for a slight increase in the number of genera found with the collecting time Figs 2A C As for abundance higher taxa richness was generally found with the second method Comparing the number of genera found per season a higher number was found in the Rio Uvita in the dry season Fig 2A but more genera were collected in the rainy season in the Rio Balso and the Rio San Lorencito Fig
20. ntropus sp Xiphocentronidae Gen sp Lepidoptera Pyralidae Petrophila sp Family non det Coleoptera Dryopidae Dryops sp Elmidae Austrolimnius sp Elmidae Cylloepus sp Elmidae Disersus sp Elmidae Heterelmis sp Elmidae Hexacylloepus sp Elmidae Hexanchorus sp Elmidae Macrelmis sp Elmidae Neoelmis sp Elmidae Phanocerus sp Elmidae Pharceonus sp Elmidae Xenelmis sp Curculionidae Gen sp Lutrochidae Lutrochus sp Psephenidae Psephenops sp Psephenidae Psephenus sp Ptilodactylidae Anchytarsus sp Staphylinidae Gen sp Diptera Athericidae Atherix sp Ceratopogonidae Atrichopogon sp Chironomidae Empididae Hemerodromia sp Empididae Neoplasta sp Psychodidae Maruina sp Simuliidae Simulium sp Stratiomyidae Gen sp Tipulidae Limoninae Gen sp Tipulidae Gen sp Tipulidae Hexatoma sp Tipulidae Limonia sp Tipulidae Molophilus sp Tipulidae Tipula sp 262 R o Uvita R o Balso R o San Lorencito X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 TABLE 2 Continued Aquatic macroinvertebrates collected in Rio Uvita Rio Balso and Rio San Lorencito in both seasons with both methods Taxa Rio Uvita Rio Balso Rio San Lorencito Other non insect groups Collembo
21. ore individuals were found with a shorter collecting time may be explained by the following 1 When a hot spot of diversity like a leaf packet was collected in a short time sample the number of individuals was rela tively high while this is evened out in the 8 or 10 min sample where poor areas such as sand banks were also included 2 Flying insects such as adult Coleoptera especially Elmidae could have escaped from the net while collecting for a longer time and small aquatic macroinverte brates such as Trichoptera and Diptera larvae especially the very small stages could crawl through the meshes 3 When collecting for 8 or 10 min the net became packed with inorganic and organic material so that it became difficult to keep the following material in the net 4 266 Voracious predators such as Megaloptera or Odonata larvae were observed feeding on other macroinvertebrates after being collected even when 70 alcohol was added to the collecting bowl 5 Perhaps the greatest problem was the transportation from the field to the laboratory since the inorganic material such as stones and sand may have ground the fragile macroinver tebrates This damage often makes identifica tion difficult The slight increase in the number of genera found with the amount of time collected could be due to the greater amount of microhabitats sampled since a greater area was covered with a higher sampling time That would also explain
22. otal collecting time of 120 minutes and preserved immediately with 70 alcohol In order to obtain species accumulation curves for this method subsamples were taken every 15 minutes The data analysis showed that the abundance and taxa richness was higher with the second method and a higher number of genera could be found with increasing collecting time but not necessarily a higher number of individuals A difference in the number of individuals between rainy and dry season was observed Species accumulation curves for samples taken with both methods showed that new genera and families were still being found after the maximum time of collection no matter which season or river Categories of water quality obtained from the BMWP CR index varied greatly among sampling times and methods used The second method always achieved a higher water quality than the longest sampling time 10 min in the first method However it still didn t reach the level obtained for all families found in both methods combined Although the first method is the one officially used in most sampling protocols for biomonitoring in temperate zones these results suggest that more extensive testing of adequate sampling time and methodology is still necessary for tropical rivers Rev Biol Trop 56 Suppl 4 257 271 Epub 2009 June 30 Key words biomonitoring aquatic macroinvertebrates water quality species accumulation curve river ecology Costa Rica Many studies have been per
23. recommended 5 or 8 min is chosen for biomonitoring it is necessary to take sev eral replicates More investigation is needed in order to find out which would be the optimal number of replicates and sampling time to adapt biomonitoring methods used in temperate areas to tropical environments ACKNOWLEDGMENTS We thank Gerardo Uma a Villalobos and Federico Bola os Vives for the support with the statistical analysis Paul Hanson for revis ing earlier drafts of the manuscript and the anonymous referees for their comments The DAAD Germany partially supported this work financially This work is a contribution to the Museo de Zoolog a Escuela de Biolog a Universidad de Costa Rica RESUMEN En zonas templadas los macroinvertebrados acu ti cos han demostrado de ser una herramienta til en los estu dios de calidad de agua y el biomonitoreo Recientemente se han realizado esfuerzos para adaptar estos m todos a los ambientes tropicales sin embargo a n existen dudas sobre la metodolog a y el tiempo de recolecta m s adecuados En el presente trabajo tres r os uno en la provincia de Alajuela y dos en Puntarenas fueron estudiados con dos m todos y diferentes tiempos de recolecta tanto en poca lluviosa como en poca seca El primer m todo incluy la recolecta de materia org nica e inorg nica por un tiem po fijo 3 5 8 10 min con un colador El material fue transferido a un recipiente pl stico con alcohol al 70
24. s necessity the study of aquatic insects has escalated in Costa Rica in the past ten years but there is still relatively little litera ture available A first step that helps avoiding misidentification of aquatic insects lies in the establishment of a reference collection and the publication of a list of the taxa encountered in the different aquatic systems Springer 1998 This represents an invaluable resource for biomonitoring studies among others There are only a few publications on biomonitoring in Costa Rica and other Central American countries eg Charpentier and Tabash 1988 Michels 1998 Paaby ef al 1998 Fenoglio et al 2002 Mafla Herrera 2005 and the neces sity for calibration of methodologies used in tem perate rivers and streams to tropical conditions has been realized and documented Fenoglio et al 2002 Stein et al 2008 Because of its impor tance limnologists and biologists in Costa Rica have focused more and more on biomonitoring over the past five years but no standard method has yet been developed Therefore this investi gation seeks to compare two different method ologies and the effect of sampling time in order to find the most efficient and useful method and the most effective time of collecting One aspect of the methodology that is still unknown is how much time is required to obtain adequate repre sentation of the local insect biota and if there are any differences in the effectiveness of collect
25. the material including the insects In the laboratory the material was searched for benthic macroinvertebrates which were placed in vials containing 70 alcohol for later identification The second method combines collecting and sorting of aquatic macroinvertebrates in the field The total collection and sample pick ing time was 120 min at each river During this time span the material was collected with the net and the specimens sorted out with forceps and placed in glass vials with 70 alcohol for later identification in the laboratory Each 15 min a new vial was used dividing the total col lection time of 120 min into eight sequences 15 min 30 min 45 min 60 min 75 min 90 min 105 min and 120 min This method is the common method used for field projects by students and researchers in the Biology School at the University of Costa Rica Identification The collected specimens were sorted and identified to the genus level with exception of Chironomidae Diptera with the aide of a dissecting microscope specialized literature and identification keys Roldan 1996 Merritt and Cummins 1996 Springer and Hanson in prep All specimens are deposited in the aquatic entomology collec tion at the Museo de Zoologia Universidad de Costa Rica BMWP CR index The BMWP index Biological Monitoring Working Party was developed by Alba Tercedor and S nchez Ortega 1988 based on the original index first described by Hellawell
26. the separation in the laboratory of a single sample can take up to 5 h With the second method one needs 2 h to collect in the field but the separation time is omitted so that the second method can be considered the more efficient and more effective method both in the expenditure of human labor and the results On the other hand the results obtained with this methodology could certainly depend on the experience of the person who collects the sample Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 160 140 120 Rio Uvita 100 m R o Balso 80 A R o San Lorencito BMWP CR index 60 40 20 3 5 8 10 60 120 Total Collecting minutes 180 160 140 120 O R o Uvita 100 W R o Balso 80 BMWP CR index A R o San Lorencito 60 40 20 3 5 8 10 60 120 Total Collecting minutes Fig 7 Values from the BMWP CR index for each river and method a rainy season b dry season Colours represent water quality levels as defined in Table 1 Rev Biol Trop Int J Trop Biol ISSN 0034 7744 Vol 56 Suppl 4 257 271 December 2008 269 In summary it can be concluded from this study that the second method where the individuals were sorted out directly in the field for a time of 120 min is the one that better represents the taxonomic diversity of a given site and therefore its water quality If the first method
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