Using transplantation to restore seagrass meadows in a protected South African lagoon.

Background: Seagrass meadows provide valuable ecosystem services but are threatened by global change pressures, and there is growing concern that the functions seagrasses perform within an ecosystem will be reduced or lost without intervention. Restoration has become an integral part of coastal management in response to major seagrass declines, but is often context dependent, requiring an assessment of methods to maximise restoration success. Here we investigate the use of different restoration strategies for the endangered in South Africa.

Effects of COVID-19 lockdowns on shorebird assemblages in an urban South African sandy beach ecosystem.

Human pressures are pervasive in coastal ecosystems, but their effect magnitudes are masked by methodological limitations. Government lockdowns associated with the global COVID-19 pandemic can address this gap since lockdowns are effectively manipulations of human presence in ecosystems at scales unachievable otherwise. We illustrate this using a study on shorebirds in an urban South African sandy beach ecosystem.

Isotopic niche size variability in an ecosystem engineer along a disturbance gradient in a South African lagoon.

A key challenge for natural resource management is how to detect effects of environmental stress on individuals and populations before declines in abundance occur. Variability in carbon and nitrogen isotope composition (δC and δN) among consumers can provide information on the population trophic niche and how it may change in response to environmental stress. We measured δC and δN values in primary producers and in an ecosystem engineer, the bioturbating sandprawn Kraussillichirus kraussi, in Langebaan Lagoon, South Africa, along a human disturbance gradient.

Fatty acid analyses provide novel insights on hippo defecation and consequences for aquatic food webs.

By defecating grasses into aquatic systems at massive scales and intensities, hippos can initiate complex changes to aquatic ecosystems. However, consequent effects on food webs are not well understood, particularly regarding shifts in basal resource contributions to consumer diets and their physiological condition. Here, we use fatty acid analysis to show that dense hippo aggregations and high dung loading are associated with (1) alterations to basal resource pools, (2) reduced quality of sediment organic matter and (3) increases in terrestrial and bacterial biomarker levels, but declines in those of diatoms in estuarine secondary consumers.

Water filtration by burrowing sandprawns provides novel insights on endobenthic engineering and solutions for eutrophication.

Managing coastal ecosystems and preserving socio-ecological functioning require a comprehensive understanding of ecological services provided by resident organisms. Here, we provide novel information on water-filtration activities of endobenthic sandprawns (Callichirus kraussi), which are key ecosystem engineers in South African coasts. We demonstrate experimentally that benthic engineering by sandprawns reduces phytoplankton biomass by roughly 50%.

Eutrophication overrides warming as a stressor for a temperate African seagrass (Zostera capensis).

Despite knowledge that seagrass meadows are threatened by multiple global change stressors, significant gaps exist in current knowledge. In particular, little is known about the interactive effects of warming and eutrophication on seagrasses globally, or about responses of African seagrasses to global change, despite these ecosystem engineers providing critical goods and services to local livelihoods. Here, we report on laboratory experiment assessing the main and joint effects of warming and nutrient enrichment on Cape eelgrass (Zostera capensis) from the West coast of South Africa, in which morphological attributes, photosynthetic efficiency and elemental content were assessed.

Declines in benthic macroinvertebrate community metrics and microphytobenthic biomass in an estuarine lake following enrichment by hippo dung.

Hippos transfer massive quantities of trophic resources from terrestrial to aquatic ecosystems through defecation. The ramifications of the latter for the functioning of benthic ecosystems are unknown, but are dependent ultimately on rates of utilisation relative to inputs. Low input and high utilisation can strengthen bottom-up pathways and enhance consumer biomass and abundance.