Gladstone megaherbivore exclusion data 2017

Full description

Gladstone megaherbivore exclusion study carried out at South Trees seagrass meadow from August to November 2017.

Abstract [Related Publication]: Grazing by all members of an herbivore community can act to structure the ecosystems they feed on. The outcome of this grazing pressure on the plant community also depends on the interaction between different herbivore groups that are present. We carried out a three-month multi-level field exclusion experiment to understand how different groups of herbivores act both individually and interactively to structure a subtropical seagrass meadow in the Great Barrier Reef. Megaherbivore grazing had the largest impact on this seagrass meadow, significantly reducing aboveground biomass and shoot height, whereas there was no measurable impact of meso- or macroherbivores on seagrass metrics or epiphyte biomass. Megaherbivores here grazed broadly across the meadow instead of targeting grazing in one area. The principal seagrass-herbivore dynamic in this meadow is that megaherbivores are the main group modifying meadow structure, and other grazer groups that are present in lower numbers do not individually or interactively structure the meadow. We demonstrate that herbivory by large grazers can significantly modify seagrass meadow characteristics. This has important implications when designing and interpreting the results of monitoring programs that seek to conserve seagrass meadows, the ecosystem services that they provide and the herbivores that rely on them. Collectively, our results and those of similar previous studies emphasize there is unlikely to be one seagrass and herbivory paradigm. Instead, for individual meadows, their unique species interactions and differences in biotic and abiotic drivers of seagrass change are likely to have a strong influence on the dominant seagrass-herbivore dynamic.

The dataset consists of a workbook (saved in both MS Excel and Open Document formats) containing 6 spreadsheets. The first worksheet is a ReadMe file and lists the remaining worksheets and treatments as follows:

Worksheets:

Aboveground biomass: Aboveground biomass assessments from photos at the start and end of the study

Shoot height: Shoot height measurements at the start and end of the experiment

Epiphytes: Epiphyte weight per core and standardised to dry weight of seagrass in the sample

SG species composition: Shoot counts from the start of the experiment (Zc  Zostera capricorni, Hu Halodule uninervis, Ho Halophila ovalis)

Mesoherbivores: Numbers of mesoherbivores in cores at the end of the experiment

Treatments:

Con         Control

Pla         Plaster block

Car         Carbaryl block

FF         Macroherbivore frame

Fis         Macroherbivore cage

FisCar Macroherbivore cage plus carbaryl block

Meg         Megaherbivore cage

MegCar Megaherbivore cage plus carbaryl block

The full methodology is available in the publication shown in the Related Publications link below.