Data examining the effects of fertilizer addition on damselfish behavior from a before-after control impact (BACI) experiment conducted in Moorea, French Polynesia in order to understand the effects of nutrient pulse events on fish herbivory and agonism. The effects of treatments on behavior were assessed by video recording each territory with a GoPro Hero7 black for 20­–30 min immediately before applying treatments (“Day 0”) and 14 days post-treatment (“Day 14”). We assessed: 1) grazing by damselfish in their own territories, 2) grazing by roving herbivores in damselfish territories, 3) aggression towards conspecifics, and 4) aggression towards heterospecifics in each video. Data were collected and analyzed by Noam T Altman-Kurosaki of the Georgia Institute of Technology.

Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

This dataset is part of a larger study of the coral reef ecosystem in Mo’orea, French Polynesia that examines mechanisms governing interactions between damselfish, corals, and turf algae. The different analyses from the broader study are listed here, with links to these associated data in the 'Related Datasets' section below.  

Analyses undertaken include:

• Fertilizer impacts on damselfish behavior (this dataset of Damselfish behavior video)
• Fertilizer impacts on biomass plus isotopic composition of algal turfs (Damselfish turf biomass dataset 950508)
• Fertilizer impacts on coral predation and herbivory (Corallivory dataset 9xxxxxx, Herbivory dataset 9xxxxx)
• Impacts of fertilizer and caging on coral and algal growth (Coral growth dataset 9xxxxx, Algal overgrowth dataset 9xxxxxx)
• Coral-turf allelopathy (Turf extracts PAM dataset 949219, Coral-algal contact dataset 9xxxxxx)
• Species composition of turf gardens (dataset 949552 + supplemental for Coral Reefs paper)

This dataset presents results examining the effects of fertilizer addition on damselfish behavior from a before-after control impact (BACI) experiment. We identified 15 spatially blocked pairs of Stegastes nigricans (damselfish) territories and into one randomly determined territory of each pair we attached a nylon mesh pouch filled with 50 grams of Osmocote slow-release fertilizer (14:14:14 NPK) directly to the substrate using u-nails. In the other plot of that pair, we attached a nylon pouch filled with 50 grams of sediment collected nearby as a physical control. All territories were at a depth of < 3 m. Pairs were ~20 meters from each other, with blocked pairs separated by > 20 meters. We measured territory size following Blanchette et al. (2019) by measuring the length, width, and height of the territory. The number and size (to the nearest centimeter) of all damselfish within each territory were estimated visually.

The treatments' effects on behavior were assessed by video recording each territory for 20­–30 minutes immediately before applying treatments (“Day 0”) and 14 days post-treatment (“Day 14”). Small video-cameras (Go-Pro Hero 7 Black) were mounted on dive weights that could be placed unobtrusively on nearby substrates. We ignored the first 5 minutes of each video to minimize the impact of camera placement on behavioral observations. Because damselfish tend to chase other herbivores from their territories, we assessed: 1) grazing by damselfish in their own territories, 2) grazing by roving herbivores in damselfish territories, 3) aggression towards conspecifics, and 4) aggression towards heterospecifics in each video. Behaviors were quantified for all resident damselfish that were visible for at least 50% of the video for each territory (i.e. not concealed in crevices or behind reef structure) and all behaviors (i.e. the number of bites or chases made by an individual fish) were standardized by the length of time that any damselfish was visible and the area of the territory at the timepoint a video was taken (i.e., Day 0 or Day 14). All behaviors were compared using generalized linear mixed effects models (GLMER) with timepoint, treatment, and their interaction as fixed effects, as is standard in BACI designs. Territory ID was nested within spatial blocking as a random effect to account for pseudoreplication from both observing multiple fish within a territory and observing the same territory over two timepoints. Within factor pairwise comparisons were conducted using the emmeans package in R (Lenth, 2023). Preliminary data visualization suggested that behavior data could be zero-inflated or overdispersed, so all behaviors were modeled using i) a Poisson family, ii) a Poisson family with a zero-inflated intercept, and iii) a negative binomial. Model assumptions for all families were assessed using DHARMa (Hartig 2022), and models were compared using the Second-order Akaike’s Information Criterion (AICc) using the MuMIn package in R (Bartoń 2024). The top model that satisfied model assumptions was then used for each behavior. Damselfish bite rate data were overdispersed, so were modeled using a negative binomial distribution. Bite rates from non-damselfish herbivores and heterospecific chase rates were both zero-inflated, so were modeled as a zero-inflated Poisson regression. Conspecific chases were modeled using a standard Poisson regression.

Changes in traits of damselfish turfs and biomass were assessed by collecting six samples of turf that were about two centimeters square (~2 cm2) using a hammer and chisel from each damselfish territory both pre- and 14 days post-treatment. Weights, ash-free dry weights, and isotopic compositions were determined to assess and describe the turf biomass. Full details can be found in BCO-DMO dataset 950508 "Damselfish Turf Biomass". (See Related Datasets section below).

Behaviors were manually counted by viewing each video several times. 

All behaviors were compared using generalized linear mixed effects models (GLMER) with timepoint, treatment, and their interaction as fixed effects, as is standard in BACI designs.

R packages emmeans, Dharma, and MuMIn were used for analysis

Coverage: Moorea, French Polynesia, South Pacific Ocean (17º32’S 149º50’W)

NSF Award Abstract:
Coral reefs are extremely diverse, supply critical ecosystem services, and are collapsing at an alarming rate, with 80% coral loss in the Caribbean and >50% in the Pacific in recent decades. Previous studies emphasized negative interactions (competition, predation) as structuring reef systems, but positive interactions in such species-rich systems could be of equal importance in maintaining ecosystem function. If foundation species like corals depend on positive interactions, then their fitness may decline with the loss of surrounding species, creating a biodiversity meltdown where loss of one coral causes losses of others. This project conducts manipulative field experiments to understand the role of coral biodiversity in facilitating coral growth, survival, resilience, and retention of these foundation species and the critical ecosystem services they provide in shallow tropical seas. This project is committed to: 1) Educating and exciting influential business and civic leaders about conservation and restoration of coastal marine systems before these systems lose ecological function and value. This will involve influential Rotary clubs within North Georgia/Atlanta (the major economic engine of the southeastern US) as an initial focus. 2) Using the Research News and Institute Communications Office at Georgia Tech and well-developed contacts with science writers to produce popular press pieces on important ocean ecology discoveries emerging from these studies. (3) Organizing a public workshop of internationally prominent scientists focused on Maintaining Marine Biodiversity as a Strategy to Sustain Ecosystem Services and Coastal Cultures and Economies. A previous effort like this, organized by the investigators, attracted about 200 attendees and was webcast to numerous high schools in Georgia and to foreign investigators in less developed countries that could not attend. Speakers also conducted in-person video interviews with local high school classes. Due to that success, this model will be repeated. 4) Working with an association of educators and cultural leaders in French Polynesia to produce electronic format presentations on our work and on reef conservation that are appropriate for use by both teachers and leaders within Polynesian culture.

Ecologists have excelled at demonstrating the importance of direct (often negative) interactions among species pairs. However, when these interactions occur in a complex context among thousands of other species in the field, the sum of the many, poorly-known, indirect interactions can counterbalance, or even reverse, the better-known direct interactions, generating diffuse mutualisms instead of agonistic outcomes. In a proof-of-concept initial experiment, coral growth and survivorship were greater in coral polycultures than monocultures, especially during early stages of community development. Processes generating this outcome are unclear but understanding these is of critical importance as diversity and function of reefs decline and as humans need to predict and adapt to changing environments. This interdisciplinary investigation merges expertise in experimental field ecology, chemical ecology, and the ecology of microbiomes to investigate the functional role of biodiversity in coral reef ecosystems. Experiments use a novel coral transplantation method and field manipulations to assess: 1) whether greater coral species diversity enhances coral community performance, as well as growth and survivorship of individual corals, 2) whether greater genotypic diversity enhances coral performance within a species, 3) whether greater diversity of seaweed competitors further suppresses corals and enhances seaweed performance, and 4) the processes driving the patterns documented above, including the roles of disease, intraspecific versus interspecific competition, predators, mutualists, and differential access to, or use of, resources. The research investigates the relationship between biodiversity and ecosystem function across dimensions of coral taxonomic diversity, from species to genotypes, and creates a series of experiments elucidating general principles underlying ecosystem dynamics. Filling these knowledge gaps advances our fundamental understanding of how biodiversity influences ecosystem function at multiple scales and provides insight into the processes promoting coral coexistence in these species-rich ecosystems. Findings will have practical implications for coral management and restoration and may improve predictions regarding coral reef resilience and recovery in the face of changing climate.