Macroalgae removal and coral larval seeding experiments on Magnetic Island 2018-2020 (NESP TWQ 4.3, JCU).

This dataset consists of monitoring data from macroalgae removal and larval seeding experiments in Florence and Arthur Bay at Magnetic Island, Queensland, Australia, collected between 2018-2020. There were twelve 5x5m permanent plots in each bay; three with macroalgae removal only, three with larval seeding only, three with macroalgae removal and larval seeding and three control plots. These data include: 
- Stationary point count fish survey data 
- Photo quadrats 
- Coral recruitment to settlement tiles
- Macroalgae frond height, holdfast presence and biomass removed

The first phase of the project (2018-2019) was macroalgae removal only, with six permanent plots in each bay (three removal, and three controls). The second phase, beginning in July 2019, included six additional plots in each bay (n=12 plots per bay) and an additional experimental treatment in Arthur Bay only, where settlement-ready coral larvae were added to six of the plots per bay (n=3 plots per treatment). In Florence Bay, upon addition of the six new plots, the six original plots were re-assigned within the algal removal treatments (n=6 plots per treatment). Original plots in Arthur Bay maintained their designation of removal / non-removal, and these designations were then superimposed with larvae / no larvae. 

Methods:
- Fish surveys: Fifteen-minute stationary point counts (SPC) with all fish present recorded, followed by a cryptic crawl (CC) consisting of five-minute search for additional species within the plot. Data was collected from March 2019 to February 2020 (4 surveys).





Photos: Three quadrats in each bay were randomly assigned for macroalgae removal and the remaining three were left untouched, representing control quadrats. Each quadrat was divided into 25 squares (1x1 m) using transect tapes, which form a gridline formation, and these squares were photographed using a digital camera at a distance of approximately 1 m above the region of interest at each survey time point. Reef benthic monitoring photographs were obtained at all quadrats (n=12) prior to macroalgae removal as a baseline in October 2018 and were recorded again immediately after manual removal of macroalgae from three of the quadrats in each bay (n=6). Four subsequent reef monitoring photograph surveys were conducted between November 2018 and May 2019. A total of 1650 photographs were obtained for this survey period.




Natural Recruits: Within the twenty-four 5x5m plots, three replicate 1x1m quadrats were haphazardly placed. All coral recruits up to 4cm were counted within the 1m2 quadrat and categorised as “branching” or “other” morphology. Recruits were also measured and categorised by diameter (i.e. 0-1cm, 1-2cm, 2-3cm, and 3-4cm). For treatment (i.e. algal removal) plots, this process was completed both before and after algal removal. 




Recruit and lab reared tiles: Terra cotta tiles were used as a proxy for bare substrate, and were installed on the reef approximately 6 weeks prior to the mass spawning event in 2018 and 2019. Following the 2018 spawning, tiles were removed at two time points – February and March 2019 – to assess recruitment success and growth between control and removal plots. Upon removal, tiles were soaked for 48 hours in a 5% sodium hypochlorite solution. Coral skeletons were counted, measured, and photographed using a Nikon SMZ745T photo-microscope. Prior to the 2019 spawning, twenty adult coral colonies were removed from Horseshoe Bay, Magnetic Island and used as broodstock. These twenty colonies were maintained in aquaria at the National Sea Simulator at AIMS. Their spawn was collected, allowed to fertilise, and cultured in aquaria for 5 days. The competent larvae were released into specialised underwater tents into each of six treatment plots (3 with algal removal, 3 without) in Arthur Bay. An initial settlement check was performed by removing the settlement tiles and examining them under a microscope, counting all recruits, and placing the tiles back into the plots. Recruit counts were repeated in February and October 2020. 




Macroalgae: Three 1x1m squares were haphazardly selected within each plot and the total number of macroalgae holdfasts recorded by divers. Algal height was measured for 10 algal fronds (from holdfast to end of frond). Biomass was the wet weight of algae removed from the removal plots.  



Limitations of the data:
- Fish: Surveys were only done during daylight hours, so nocturnal fish are likely to have been missed, visibility was low at times making it harder to see fish, cryptic fishes are often missed during visual surveys. 





Photo quadrats: Algae canopy can make it difficult to estimate benthic cover, ID challenges in general, low visibility makes it challenging to get clear photos.




Recruits: Bleaching method doesn’t allow to see if a recruit was alive when sampled; settlement tiles are not exact analogues to natural reef environment; some tiles were lost or tampered with.




Algae: Macroalgae were not identified to species level, it can be hard to define what a holdfast is. 



Format:
This dataset consists of four spreadsheets datasets associated with the ecology and community composition of the experiments. 

1_Fish_Data
Fish community data from underwater surveys

2_Photo_Quadrats
Photos showing benthic cover (coral, macroalgae etc.) within experimental plots

4_Natural_Recruits
Coral recruits to tiles within experimental plots without larval seeding 

5_Recruit&amp;Lab-reared_Tiles
Coral recruits to tiles for the larvae seeding experiments

6_Macroalgae
Macroalgae frond height, number of holdfasts and biomass of removed macroalgae

Data Dictionary:
Fish surveys:
File: Fish - macroalgae removal experiments magnetic island.xlsx [2 datasheets: Stationary Point Count (SPC) &amp; Cryptic Crawl (CC)]
- Date: Date of survey
- Time: Survey start time
- Bay: Two sites on Magnetic Island were surveyed - Arthur and Florence Bays
- Plot: Fixed plot number surveyed at each of 2 sites
- Treatment: Control, Removal only, Larvae, Removal and larvae
- ID: sample/quadrat photo ID
- Visibility (m): water visibility assessed by diver at start of dive 
- Species: Fish species observed
- Count: Total number of fish of each species observed
- Observer: Name of diver recording fish data

Natural Recruits:
*Note that this part of monitoring commenced in the “Study” phase, so no pilot data exists (nor does the column specifying study phase)
File name: Recruits.csv
- LOCATION: Two sites on Magnetic Island - Arthur and Florence Bays
- PLOT: Fixed plot number surveyed at each of 2 sites
- DATE: Date of survey
- QUADRAT: Replicate 1x1m square quadrat within each experimental plot
- TREATMENT: Treatment, macroalgae removal, larval enhancement, both or none. 
- PRE-POST: when the survey was conducted, either pre- or post-removal of algae
- SIZE: categories of recruit diameter where 1=0-1cm; 2 = 1-2cm; 3 = 2-3cm, 4 = 3-4cm
- MORPHOLOGY
- COUNT: number of coral recruits observed
- OBSERVER: The person who made the observation

Lab-reared recruits:
File name: LabRearedRecruits.xlsx [2 datasheets: Treatment &amp; Control]
- Sort: Individual identifier
- Plot: Plot number
- Treatment: Experimental treatment
- Tile: Tile number
- Surface: side of the tile where recruits were counted
- Acroporidae: Number of recruits from the family Acroporidae
- Total per tile: Total number of coral recruits per tile
- Mean per tile plot: Mean number of coral recruits per tile within a plot
- Mean per tile: Mean number of coral recruits per tile 
- Pocilloporidae: Number of recruits from the family Pocilloporida
- Others: Number of coral recruits from other families

Macroalgae:
File name: Holdfasts.csv
- BAY Two sites on Magnetic Island - Arthur and Florence Bays
- PLOT Fixed plot number surveyed at each of 2 sites
- HOLDFASTS The number of Sargassum holdfasts counted in each 1x1m replicate 
- DATE: date of survey
- TREATMENT: Treatment of macroalgae removal, larval enhancement, both or none.
- PRE/POST: when the survey was conducted, either pre- or post-removal of algae
- OBSERVER: the person making the observation
- STUDY-PHASE: either Pilot or Study. Pilot phase included 6 plots per bay, while Study phase included 12 plots per bay. Furthermore the plot treatment designations were changed in Florence Bay between Pilot and Study phases. 
- NOTES: miscellaneous text

File name: Biomass.xlsx
- BAY:  Two sites on Magnetic Island – Arthur and Florence Bays
- PLOT: Fixed plot number surveyed at each of 2 sites
- DATE: date of survey
- TREATMENT: Treatment of macroalgae removal, larval enhancement, both, or none
- KG: Kilograms of wet weight macroalgae removed from each experimental plot, weighed to the nearest 0.1kg using fish scales. 
- OBSERVER: The person making the observation

File name: Algae.csv
- BAY: Two sites on Magnetic Island – Arthur and Florence Bays
- PLOT: Fixed plot number surveyed at each of 2 sites
- QUADRAT: Replicate 1x1m quadrat within each plot being surveyed. Three replicates per plot.
- FROND: Replicate number of frond measurement, 1-10
- HEIGHT: Height of the algal frond from holdfast to frond tip, measured in cm.
- DATE: Date of survey
- TREATMENT: Treatment of macroalgae removal, larval enhancement, both, or none
- PrePostRemoval: when the survey was conducted, either pre- or post-removal of algae
- OBSERVER: the person making the observation
- STUDY-PHASE: either Pilot or Study. Pilot phase included 6 plots per bay, while Study phase included 12 plots per bay. Furthermore the plot treatment designations were changed in Florence Bay between Pilot and Study phases. 
- NOTES: any miscellaneous text

eAtlas Change Log:
Updated 04-Oct-2024 to remove embargo and update data links.

Data Location:

This dataset is filed in the eAtlas enduring data repository at: data\nesp4\4.3_Best-practice-coral-restoration\

Organization: Australian Ocean Data Network