Defense Date
8-5-2025
Document Type
Thesis
Degree Type
Master of Science
Degree Name
Marine Science
First Advisor
Joana Figueiredo
Second Advisor
D. Abigial Renegar
Third Advisor
Chris Langdon
Keywords
grow-out, survival, ex situ, N:P ratio, Montastraea cavernosa, Pseudodiploria clivosa, orientation, phosphate
Abstract
As coral reefs keep declining, it is imperative to increase coral production ex situ for restoration, but this requires culture protocols to be optimized. This study examined the impacts of grow-out orientation and phosphate concentration (and nitrate (N): phosphate (P) ratio) on the survival and growth of Montastraea cavernosa and Pseudodiploria clivosa juveniles from 3 to 9 months old. Pristine reefs typically have low nitrate (0.12μmol/L) and low phosphate (0.03μmol/L) concentrations, leading to N:P ratios of 4-16 N: 1P. In recirculating tanks, it is difficult to lower nitrate concentrations below 25μmol/L. Here we hypothesized that increasing the phosphate concentration in aquaria while keeping nitrate concentration high to reach the optimal N:P will enhance coral survival and growth. We assessed this by using two phosphate concentrations, 4.04 ± 0.08μmol/L and 2.43 ± 0.03μmol/L, while keeping nitrate concentration at 39.11 ± 0.71μmol/L, leading to N:P ratios of 10:1 and 16:1. We also investigated the influence of diagonal (60°), horizontal (0°) and vertical (90°) orientation on coral grow-out. Growing corals out at an angled orientation reduced detritus accumulation and doubled the number of corals that could be reared in the same space. It also resulted in significantly higher survival rates for M. cavernosa (73.82 ± 7%) and P. clivosa (89.53 ± 5%), compared to the horizontal orientation (62.35 ± 7% and 65.35 ± 9%, respectively per species). Corals grown at the high phosphate concentration (10:1 N:P ratio), had significantly larger final live tissue area than corals grown in the low phosphate concentration. When considering both survival and growth our findings suggest that M. cavernosa and P. clivosa juveniles from 3 to 9 months of age should be grown ex situ at a diagonal orientation under a high phosphate (4.04 μmol/L) concentration within a 10:1 N:P ratio.
NSUWorks Citation
Ashley Shen. 2025. The benefits of high phosphate concentration (10N : 1P) and diagonal orientation on the ex situ grow-out of Caribbean coral juveniles. Master's thesis. Nova Southeastern University. Retrieved from NSUWorks, . (216)
https://nsuworks.nova.edu/hcas_etd_all/216.
Comments
Could you please ensure my title has the words "ex situ" italicised. I am unable to add it on this end.