Isotopic variation in five species of stream fishes under the influence of different land uses

Abstract

The aim of this study was to test if changes in land use alter the isotopic signature of fish species, promoting changes in the trophic position and food resource partitioning between these consumers. Three different systems were investigated: pasture streams (n = 3), streams in sugar cane plantations (n = 3) and reference streams (n = 3). Fish species Aspidoras fuscoguttatus, Astyanax altiparanae, Characidium zebra, Hisonotus piracanjuba and Knodus moenkhausii were selected, and their nitrogen and carbon isotopic compositions were estimated to assess changes in the trophic level and partitioning of food items consumed. The composition of δ(13) C (‰) only differed among the land use categories for A. altiparanae, H. piracanjuba and K. moenkhausii. Resource partitioning was different for all species, with changes in the sources or proportions they consumed in each land use category, but only A. altiparanae introduced new food sources in large quantity in altered land uses. It is important to note, however, that the results from the resource partitioning analysis are limited due to large overlapping of isotopic signatures between the analysed food resources. All fish species exhibited variation in δ(15) N (‰), with the highest values found in streams under sugar cane or pasture influence. Despite the variation in nitrogen isotopic values, only C. zebra and H. piracanjuba displayed changes in trophic level. Therefore, it is believed that the increase in the δ(15) N (‰) value of the individuals collected in streams under the influence of sugar cane or pasture was due to the greater influence of livestock dung and chemical and organic fertilizers. The results also highlight the importance of studying consumer species along with all forms of resources available at each location separately, because the signatures of these resources also vary within different land uses.

Can mussels be used as sentinel organisms for characterization of pollution in urban water systems?

“…mussels) Cabana and Rasmussen, 1996;Harrington et al, 1998;Oczkowski et al, 2008;Carvalho et al, 2015). In addition and identical to our study, the range of δ 15 N values for nitrate and POM has been shown to be wider than the range for primary producers, indicating a timeaveraging effect in mussels (Gustafson et al, 2007;Wang et al, 2013).…”

“…Stable isotopes of nitrogen (N), carbon (C), sulfur (S), and oxygen (O) in water and biota have also been applied as an integrated measure of ecosystem processes (Robinson, 2001;Chaves et al, 2003;Pace et al, 2004). Furthermore, the analysis of the nitrogen signature has proven to be an especially powerful tool as an indicator of anthropogenic contamination (Lake et al, 2001;McKinney et al, 2002;Fry and Allen, 2003;Xu and Zhang, 2012) and land use (Harrington et al, 1998;Broderius, 2013;Carvalho et al, 2015), bearing on the fact that the sources of contamination such as animal manure, sewage, septic waste, and some fertilizers carry higher nitrogen signatures values and consequently a higher δ 15 N (Heaton, 1986;Cabana and Rasmussen, 1996;Kellman, 2005;Choi et al, 2007). This signal is then passed on to higher trophic levels up the food chain Carvalho et al, 2015): elevated δ 15 N signals in nitrate have been shown to lead to elevated δ 15 N signals in organisms that directly take up nitrate from the water, such as phytoplankton and microbes (Harrington et al, 1998).…”

Changes in trophic characteristics of two fish species of Astyanax (Teleostei: Characidae) in response to aquatic pollution

“…One way to identify how distinct species respond to changes in the environment is by comparing their feeding habits in regions under differing levels of human disturbance (e.g, Carvalho et al 2015). Accordingly, analyses of stomach contents and stable isotopes (carbon and nitrogen), can be used simultaneously for robust and reliable assessment of feeding habits (e.g., Carassou et al 2017, Connan 2017.…”

Diet composition changes in tigerfish of Lake Kariba following an invasion by redclaw crayfish

“…It has also proven a useful tool in elucidating patterns of resource allocation (Bergamino et al, 2014) and in the construction of food webs within ecosystems because it provides time-and space-integrated insights into trophic relationships among organisms (Hansson et al, 1997;Fry and Davis, 2015). This technique is particularly suited to determining the relative contributions of two isotopically distinct sources of organic matter to the diets of consumers and yields time-integrated information of assimilated not just ingested foods (Vander Zanden et al, 1997;Layman et al, 2012;Carvalho et al, 2015). The foundation of stable nitrogen isotopes is that the ratio between 15 N and 14 N in biological tissues is variable, and the proportion of 15 N usually increases with the increasing trophic level (Hansson et al, 1997).…”