Associations between estuarine foundation species and their effect on biodiversity across latitudes and seasons [article]

Derek Albert Gerber, University Of Canterbury
Seagrass, seaweed, and bivalves are ubiquitous foundation species in estuarine ecosystems that often have positive impacts on biodiversity. However, relatively little is known about their distribution patterns on the South Island of New Zealand (specifically, Zostera muelleri, Ulva spp. and shell deposits from the ubiquitous cockle Austrovenus stutchburyi) and their effects on local biodiversity across spatiotemporal scales. To address this research gap, nine estuaries were sampled in winter
more » ... 0 across tidal elevations and along a latitudinal gradient from 41°S to 46 °S, and in two estuaries around the Banks Peninsula (every month from November 2020 to October 2021). Small- and large-scale sampling methods were used to quantify co-occurrence patterns between foundation species (Chapter 2) and their effects on associated plant and animal communities (Chapter 3) in both the latitudinal and seasonal surveys. Such multifactorial baseline data collected across spatiotemporal scales are important to gauge how estuaries may be affected by future stressors, like eutrophication, warming, and other anthropogenic stressors. In Chapter two, geotagged small scale digital photos and large-scale drone images were collected and analysed for percent cover of foundation species across latitudes and seasons. I found strong effects of latitude and season on the abundance of all foundation species, and results were consistent between scales. Zostera was most abundant in southern estuaries and in winter months whereas surface deposited shells were most abundant in northern estuaries and also in winter months. By comparison, Ulva was generally found in low abundances but was relatively common in the Avon Heathcote Estuary in summer months. I also found negative correlations between seaweed and seagrass suggesting that Ulva may have negative effects on Zostera, for example through competition for light or by creating adverse environmental conditions such as low oxygen levels. In Chapter three, species-habitat-associations were quantifi [...]
doi:10.26021/11369 fatcat:sxu752uhrnbv7au2js7eucsdfm