The relative importance of autochthony along the longitudinal gradient of a small South African river influenced by agricultural activities

Moyo, Sydney; Richoux, Nicole B

Title: The relative importance of autochthony along the longitudinal gradient of a small South African river influenced by agricultural activities
Creator: Moyo, Sydney
Creator: Richoux, Nicole B
Subject: To be catalogued
Date Issued: 2018
Date: 2018
Type: text
Type: article
Identifier: http://hdl.handle.net/10962/454392
Identifier: vital:75340
Identifier: xlink:href="https://doi.org/10.1016/j.fooweb.2018.e00082"
Description: Generalisations about the sources of organic matter that support aquatic consumers are usually focussed on certain parts of the world (particularly the northern hemisphere) and large rivers, and therefore may not include the full spectrum of food webs that occur in the southern hemisphere (particularly those with high nitrogen inputs). We studied the relative importance of organic matter sources to macroinvertebrate consumers in a small South African river. Based on previous observations of our system of interest and other agricultural streams, we hypothesised that (a) the carbon fuelling consumers is primarily derived from autochthonous (in situ) food sources regardless of sampling time and, (b) the contribution of autochthonous basal resources to consumers increases in importance as the river widens (from upper to downstream reaches). To test these predictions, stable carbon (δ13C) and nitrogen (δ15N) isotopes were used to estimate the contributions of local algal and land-based production to aquatic macroinvertebrates over space (six sites) and time (four sampling occasions between November 2012 and September 2013) along the Kowie River, South Africa. Mixing models revealed that consumers in the upper reaches assimilated terrestrially-derived allochthonous organic matter, and consumers in the middle and lower reaches assimilated primarily autochthonous basal resources (macrophytes and algae). The isotopic values of consumers and their food sources changed over time, indicating that food sources and consumers should be analysed many times throughout the year to capture that variability and ensure that ephemeral components of the food web are not missed. Our results enhance the growing body of literature on the dynamics of riverine systems and indicate the importance of autochthony in a small temperate river with high nitrogen inputs.
Format: computer
Format: online resource
Format: application/pdf
Format: 1 online resource (13 pages)
Format: pdf
Publisher: Elsevier
Language: English
Relation: Food Webs
Relation: Moyo, S. and Richoux, N.B., 2018. The relative importance of autochthony along the longitudinal gradient of a small South African river influenced by agricultural activities. Food webs, 15, p.e00082
Relation: Food Webs volume 15 p.e. 00082 2018 2352-2496
Rights: Publisher
Rights: Use of this resource is governed by the terms and conditions of the Elsevier Terms and Conditions Statement (https://www.elsevier.com/legal/elsevier-website-terms-and-conditions)
Rights: Closed Access

Hits: 17
Visitors: 17
Downloads: 2

Collections

Richoux, Nicole Bertine (Assoc Prof)

RU Department of Zoology and Entomology

SDG 15. Life On Land

		Thumbnail	File	Description	Size	Format
View Details Download			SOURCE1	The relative importance of autochthony along the longitudinal gradient of a small South African river influenced by agricultural activities.pdf	747 KB	Adobe Acrobat PDF	View Details Download