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Marine Ecology Progress Series

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MEPS 634:77-88 (2020)  -  DOI:

Dissolved inorganic nutrient enrichment does not affect sponge growth or condition

Blake D. Ramsby1,2,3,*, Joshua Heishman3,4, Mia O. Hoogenboom1, Steve Whalan5, Nicole S. Webster2,3,6

1College of Science and Engineering and ARC Centre of Excellence for Coral Reef Studies, James Cook University, Townsville, Queensland 4811, Australia
2Australian Institute of Marine Science, Townsville, Queensland 4810, Australia
3AIMS@JCU, Australian Institute of Marine Science and James Cook University, Townsville, Queensland 4811, Australia
4Department of Biological Sciences, College of Science, Purdue University, West Lafayette, Indiana 47907, USA
5Marine Ecology Research Centre, School of Environment, Science and Engineering, Southern Cross University, Lismore, New South Wales 2480, Australia
6Australian Centre for Ecogenomics, The University of Queensland, St Lucia, Queensland 4072, Australia
*Corresponding author:

ABSTRACT: Changing land use and an increasing human population have led to increased terrestrial runoff, which delivers nutrients, pesticides, and heavy metals into aquatic ecosystems. Elevated nutrient levels can adversely affect nearshore corals by reducing the amount of light reaching the benthos, exacerbating coral disease and bleaching, as well as stimulating algal growth, but the effects on other reef taxa are poorly understood. We investigated the effects of dissolved inorganic nutrient enrichment and changes in irradiance on the growth and condition of 5 common Great Barrier Reef sponges: 4 sponges with photosynthetic symbionts and 1 lacking photosynthetic symbionts. Concentrations of up to 7 µM total dissolved inorganic nitrogen (DIN) did not significantly affect the growth, condition, or chl a content of any sponge species after 10 wk exposure. However, 2 species lost >20% volume across all nutrient treatments, suggesting that aquarium conditions may have been suboptimal for these species. Irradiance (80 vs. 160 µmol quanta m-2 s-1) did not affect 4 of the 5 sponge species; however, higher irradiance resulted in higher organic content and chl a levels in the bioeroding sponge Cliona orientalis, the only studied species that associates with the photosynthetic dinoflagellate Symbiodinium, suggesting that sponge-Symbiodinium associations may be more sensitive to irradiance levels than sponge-Cyanobacteria associations. While elevated nutrient levels are exacerbating the decline of reef-building corals, exposure to the average DIN levels within flood plumes that reach inshore reefs appears to have negligible effects on reef sponges.

KEY WORDS: Nitrogen · Phosphorus · Light · Pollution

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Cite this article as: Ramsby BD, Heishman J, Hoogenboom MO, Whalan S, Webster NS (2020) Dissolved inorganic nutrient enrichment does not affect sponge growth or condition. Mar Ecol Prog Ser 634:77-88.

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