Method for monitoring intertidal communities in a steep rocky shore: a combination of digital image technology and field operational strategy

Abstract

A B S T R A C TThis paper introduces a method for temporal studies of steep rocky intertidal communities. It combines the use of digital image technology with field methodology, so that a wide area of the community can be sampled in a short time. Two current nondestructive percent cover estimation methods (visual estimation and point intersection) were compared in terms of cost, operational advantages and data quality, with a proposed method for a sucessional study . The proposed method used sequential photos to sample multiple fixed vertical transects over time. Reproduction of the midintertidal transect over time was possible by overlaying temporal transects in an image editing program. This method was similar to the point intersection quadrat method used to estimate percent cover. Benefits included reduced time on field work, economic advantages and other advantages of using digital photography, such as recording. Temporal photography of transects provided measurements of recruitment, mortality and population growth, and made it possible to manufacture an animation of sucessional stages. We suggest that this is the best method for providing information and understanding on the process of succession and for monitoring benthic invertebrate intertidal communities on steep rocky shores. R E S U M OEste trabalho apresenta uma metodologia para estudos temporais de comunidades entre-marés de costões rochosos com acentuada inclinação, associando tecnologia de captura de imagens digitais com uma estrutura operacional de campo, permitindo a amostragem de ampla faixa da comunidade, em pouco tempo. Dois métodos tradicionais de estimativa de porcentagem de cobertura (estimativa visual e pontos de interseção) foram usados para comparar a aplicabilidade do método proposto a um estudo de sucessão, quanto às vantagens econômicas, operacionais e qualidade dos dados obtidos. O método permite a amostragem temporal de múltiplos transectos verticais específicos, por meio de fotos seqüenciais. As mesmas são fundamentais para a posterior montagem da imagem do transecto num programa de edição de imagem através da compilação das fotos e sobreposição temporal dos transectos. Este método obteve resultados similares ao método de pontos de interseção quanto às leituras de porcentagem de cobertura, além de reduzido tempo em campo, vantagens econômicas e vantagens do uso das fotografias digitais. A análise das transições temporais permitiu a obtenção de parâmetros como recrutamento, mortalidade e crescimento populacional, além da montagem de uma animação com a sucessão. Consideramos esta metodologia a mais indicada para estudos de sucessão ecológica, especialmente no monitoramento de comunidades de invertebrados bentônicos do médiolitoral, em costões de inclinação acentuada.

Environmental DNA (eDNA) metabarcoding reveals strong discrimination among diverse marine habitats connected by water movement

“…Samples were taken immediately following high tide on 22 October 2016 within a 3-hr window to ensure the detection of intertidal species assemblages. This community was targeted for their high levels of impact by human activities (Suchanek, 1994) and their frequent inclusion in monitoring programs due to ease of sampling (Díez, Secilla, Santolaria, & Gorostiaga, 2008;Moyses, Junqueira, & Lavrado, & Silva, 2007). Immediate post-high-tide sampling also ensured a unidirectional water flow out of Otago Harbor (Old & Vennell, 2001).…”

Spatial variability in the population of Isognomon bicolor (C.B. Adams, 1845) (mollusca, bivalvia) on rocky shores in Espírito Santo, Brazil

“…Further, the individuals are more closely aggregated in the crevices, differently from the flat surfaces. Similarly, Moysés et al (2007) noted that I. bicolor, in the early stages of succession, presents an aggregate distribution colonizing only depressions of the substrate. Table 1.…”

“…The recent invasion of the Brazilian coast by Isognomon bicolor may be the result of an unintentional introduction by fouling or ballast water. Native to the Caribbean, this species currently occurs on rocky shores along the Brazilian coast (DOMANESCHI; MARTINS, 2002;FERNANDES et al, 2004;MOYSÉS et al, 2007). However, the extent of the damage caused by their introduction is unknown (FERNANDES et al, 2004).…”

Quantitative Approach to the "Physiognomic Assessment of Hard Bottom Marine Benthic Communities" Method: Precision Analysis

“…Moysés et al (2007) attributed the high precision of photographic sampling to the absence of adverse fi eld conditions, which permits devoting more attention onto the analysis.…”