A new method to quantify macroalgae and a practical sampler for experimentation in lotic habitats

Abstract

Experimental studies in rivers and streams are extremely difficult to run due to the fact that the conditions of these environments are very complex and provide a high level of heterogeneity, which hinders the precise control and standardization of variables. In this study, we present a practical sampler that was designed to make it easier to conduct research projects involving benthic communities of lotic environments, as well as a new nondestructive technique for quantification of the macroalgal communities typically found in these habitats. The sampler consists of an acrylic square tube in which water flows normally inside. This structure carries a removable glass plaque with a known area and can simulate various ecological situations by changing both biotic and abiotic conditions. Thus, it can mitigate the differences between environmental characteristics where each sampler is exposed. The new technique involves capturing digital images that can monitor a unique macroalgal community in development throughout time and a more precise quantification when compared with other techniques that are widely applied. The sampler is easy to build and the images simple to quantify, allowing the detection of spatial and temporal variations in richness and abundance of investigated communities.Keywords: artificial substrate, sampling method, stream macroalgae, limnology.Um novo método para quantificar macroalgas e um prático amostrador para experimentação em ecossistemas lóticos ResumoOs estudos experimentais em rios e riachos são extremamente difíceis de serem executados, visto que as condições desses ambientes são muito complexas e proporcionam um alto nível de heterogeneidade, o que dificulta o controle e a padronização precisa das variáveis. Nesse contexto, um prático amostrador foi desenvolvido para facilitar a execução de projetos de pesquisas envolvendo comunidades bentônicas de ambientes lóticos, além de constituir uma nova técnica não destrutiva para quantificação das macroalgas tipicamente encontradas nesses habitats. O amostrador consiste de um tubo de acrílico de seção quadrada, pelo qual a água corrente flui normalmente em seu interior. Tal estrutura porta uma placa de vidro removível com área conhecida e permite simular diversas situações ecológicas, variando tanto as condições abióticas como as bióticas, além de amenizar as diferenças entre as características ambientais a que está submetido cada um dos amostradores. Diversamente, a nova técnica consiste na captura de imagens digitais que permitem o acompanhamento temporal de uma mesma comunidade de macroalgas em desenvolvimento e uma quantificação mais precisa quando comparada com técnicas amplamente aplicadas na área. O amostrador é fácil de construir e as imagens são simples para quantificar, permitindo a detecção de variações espaço-temporais na riqueza e abundância das comunidades investigadas.Palavras-chave: substratos artificiais, método de amostragem, macroalgas de riachos, limnologia.

Microhabitat hydraulics predict algae growth in running systems

“…This period is considered suitable for algal settlement (Danger et al, 2013). The surface area coverage (SAC-%) of the biofilm in the pictures was calculated in a standardized centered area (1 cm 2 ), to avoid border effects, using Adobe Photoshop (Tonetto et al, 2012). This technique was adapted from Ng et al 2014, Singer et al (2006) and recent studies have used percent coverage as an algal metric (Tonetto et al, 2012(Tonetto et al, , 2014.…”

The effects of habitat complexity and hydraulic conditions on the establishment of benthic stream macroalgae

“…On the last day of the experiment, we took digital photographs of each tile and then measured the area occupied by macroalgae, recording it as per cent cover. These images were analysed using AutoCad software, Autodesk, Inc (San Rafael, CA, U.S.A.), which provided reliable and accurate measurements that were sufficiently sensitive to detect changes in per cent cover (Tonetto, Peres & Branco, ; Tonetto et al ., ). Water temperature, pH, dissolved oxygen, turbidity and conductivity were measured using the U‐50 multiparameter water quality checker (Horiba, Process and Environmental, Tokyo, Japan).…”

Effects of crevice size on the establishment of macroalgae in subtropical streams

“…In order to calibrate the quantification method, we used the AutoCad scale function to establish the same scale for all images. This method allowed us to increase the measurement accuracy of abundance (in terms of percent cover) of the communities in relation to other methods commonly used in ecological studies involving these algae (Tonetto et al, 2012a) For identifying the macroalgal species present on the artificial substrates, each macroalgal morphotype was examined in the laboratory with the help of a Leica DM 1000 microscope. After identification, the species were associated with its correspondent morphotype observed in the colonized plates.…”