title: Suspended sediments limit coral sperm availability.
abstract: Suspended sediment from dredging activities and natural resuspension events represent a risk to the reproductive processes of coral, and therefore the ongoing maintenance of reefal populations. To investigate the underlying mechanisms that could reduce the fertilisation success in turbid water, we conducted several experiments exposing gametes of the corals Acropora tenuis and A. millepora to two sediment types. Sperm limitation was identified in the presence of siliciclastic sediment (230 and ~700 mg L(-1)), with 2-37 fold more sperm required to achieve maximum fertilisation rates, when compared with sediment-free treatments. This effect was more pronounced at sub-optimum sperm concentrations. Considerable (>45%) decreases in sperm concentration at the water's surface was recorded in the presence of siliciclastic sediment and a >20% decrease for carbonate sediment. Electron microscopy then confirmed sediment entangled sperm and we propose entrapment and sinking is the primary mechanism reducing sperm available to the egg. Longer exposure to suspended sediments and gamete aging further decreased fertilisation success when compared with a shorter exposure. Collectively, these findings demonstrate that high concentrations of suspended sediments effectively remove sperm from the water's surface during coral spawning events, reducing the window for fertilisation with potential subsequent flow-on effects for recruitment.
authors.affiliation: Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia, 6009, Australia.|Australian Institute of Marine Science, Townsville, 4180, Queensland, and Perth, 6009, Western Australia, Australia.|Western Australian Marine Science Institution, Perth, 6009, Western Australia, Australia.|Oceans Institute, The University of Western Australia, Perth, Western Australia, 6009, Australia.
authors.forename: Gerard F
authors.initials: GF
authors.lastname: Ricardo
authors.affiliation: Australian Institute of Marine Science, Townsville, 4180, Queensland, and Perth, 6009, Western Australia, Australia.|Western Australian Marine Science Institution, Perth, 6009, Western Australia, Australia.
authors.forename: Ross J
authors.initials: RJ
authors.lastname: Jones
authors.affiliation: Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Perth, Western Australia, 6009, Australia.|Oceans Institute, The University of Western Australia, Perth, Western Australia, 6009, Australia.
authors.forename: Peta L
authors.initials: PL
authors.lastname: Clode
authors.affiliation: Australian Institute of Marine Science, Townsville, 4180, Queensland, and Perth, 6009, Western Australia, Australia.|Australian Research Centre of Excellence for Coral Reef Studies, James Cook University Townsville, Queensland, Australia.
authors.forename: Adriana
authors.initials: A
authors.lastname: Humanes
authors.affiliation: Australian Institute of Marine Science, Townsville, 4180, Queensland, and Perth, 6009, Western Australia, Australia.|Western Australian Marine Science Institution, Perth, 6009, Western Australia, Australia.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Negri
mesh_terms: D000535:Aluminum / Q000737:chemistry; D000818:Animals; D037421:Anthozoa / Q000145:classification / Q000502:physiology*; D002254:Carbonates / Q000737:chemistry; D002470:Cell Survival / Q000502:physiology; D055867:Cyclonic Storms; D017753:Ecosystem; D005260:Female; D005306:Fertilization / Q000502:physiology; D005843:Geography; D019015:Geologic Sediments / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008297:Male; D008855:Microscopy, Electron, Scanning; D010063:Ovum / Q000502:physiology* / Q000648:ultrastructure; D012307:Risk Factors; D012623:Seawater / Q000737:chemistry; D013045:Species Specificity; D013094:Spermatozoa / Q000502:physiology* / Q000648:ultrastructure; D014904:Western Australia
chemical_list: D002254:Carbonates; D000535:Aluminum; D007501:Iron