Cost/benefit and the effect of sample preservation procedures on quantitative patterns in benthic ecology

Abstract

Some benthic assemblages studies have tested the effects of different preservation procedures on biomass, but their influence on quantitative patterns (number of species and abundance) is still unclear. We evaluated the influence of two sample preservation procedures on quantitative patterns in benthic ecology. Ten sampling points were systematically interspersed on two types of sediment (sandy and muddy). At each sediment type, samples from five sampling points were fixed in 10% formalin, and the other five points were preserved in 70% ethanol (without previous fixation). Three replicates were collected at each sampling point, and samples were washed in 0.5 mesh size and sorted in laboratory. A cost/benefit analysis was performed considering the washing time in laboratory and the costs of substances. A total of 1970 individuals were collected (muddy sediment: 132; sandy sediment: 1838), belonging to 121 taxa (muddy: 49; sandy: 83). Assemblages preserved in ethanol were composed of 795 individuals and 80 taxa, while those fixed with formalin had 1173 individuals and 94 taxa. Polychaeta predominated as the most abundant group for both preservation procedures. For the whole benthic community, significant differences occurred only between sediment types. Significant differences in the number of individuals of polychaetes were observed for the different preservation procedures in sandy sediment. Ethanol has the best cost/benefit ratio in both sediment types due to additional costs to attend safety requirements for formalin-fixed samples. Further studies should evaluate how quantitative patterns are affected by exposure time of preservation, anesthesia interaction, and morphological deformations (e.g. impossibility of identification).

Efecto del tamaño de tamiz en la caracterización de la macrofauna marina bentónica: Implicancias para su uso en líneas de base, caracterizaciones preliminares de sitios para la acuicultura y monitoreos ambientales en Chile

“…La elección del tamaño de abertura es un tema debatible, ya que, si bien un tamiz grueso ayuda a retener la fracción de mayor tamaño del material recolectado, subestima el número y presencia de organismos más pequeños. Por el contrario, tamices de menor abertura pueden retener mayor cantidad de organismos, pero los costos de procesamiento debido al mayor tiempo invertido en la revisión, son más elevados ( de Souza & Barros 2017). En la actualidad, se discute sobre el compromiso tiempo/costo de diferentes opciones para el análisis de este tipo de muestras biológicas y, de la calidad/cantidad de información necesaria para evaluar adecuadamente el impacto ambiental que se haya generado o podría generarse a causa de alguna actividad antropogénica en los ecosistemas marinos (Carey & Keough 2002, Souza & Barros 2015, de Souza & Barros 2017.…”

“…Por el contrario, tamices de menor abertura pueden retener mayor cantidad de organismos, pero los costos de procesamiento debido al mayor tiempo invertido en la revisión, son más elevados ( de Souza & Barros 2017). En la actualidad, se discute sobre el compromiso tiempo/costo de diferentes opciones para el análisis de este tipo de muestras biológicas y, de la calidad/cantidad de información necesaria para evaluar adecuadamente el impacto ambiental que se haya generado o podría generarse a causa de alguna actividad antropogénica en los ecosistemas marinos (Carey & Keough 2002, Souza & Barros 2015, de Souza & Barros 2017. No obstante el uso generalizado de tamices en estudios que caracterizan la macrofauna marina bentónica, existen pocos trabajos donde se compare cualitativa y cuantitativamente los resultados obtenidos de su estructura comunitaria, considerando las ventajas y desventajas del tamaño disímil de los individuos retenidos por tamices de diferente abertura (Bachelet 1990, Edgar 1990, Schlacher & Wooldridge 1996 largos períodos de tiempo y en lugares específicos (Pearson & Rosenberg 1978, Gray et al 1988, Carrasco & Gallardo 1989, Levin et al 2001, Paul et al 2001, Dauvin 2007.…”

“…Vol. 56, N°1, 2021 Revista de Biología Marina y Oceanografía 1997, Hudson & Adams 1998, Tanaka & Leite 1998, Morin et al 2004, Lampadariou et al 2005, Souza & Barros 2015, Pino et al 2015, de Souza & Barros 2017.…”

Effects of formaldehyde preservation time on the length-weight relationship of the ubiquitous neotropical cladoceran Ceriodaphnia silvestrii

“…Size per se influences functional and ecological traits of organisms and their role in ecosystem processes (Brown et al, 2004;Woodward et al, 2005). As a result, studying the influence of body size on trophic efficiency has become a prominent focus in ecology and applied biology, emphasizing the need for accurate and efficient individual and population measurements (LaBarbera, 1989;Wetzel et al, 2005;Costa-Paiva et al, 2007;Souza & Barros, 2017). Most often, measurements are based on dry weight (e.g.…”

“…Generally, buffered formalin solution and ethanol are considered to be suitable preservatives and have been commonly used as fixative for zooplankton samples and other invertebrate groups (Souza & Barros, 2017). Nearly one hundred years ago, several studies already described deleterious effects of those preservatives on dry weight of preserved animals (e.g.…”