HCRI Project Final Report Format
I. Project Title: The invasive green macroalga Avrainvillea amadelpha on Oahu
Principal Investigator: Florence Thomas
Project Staff: Kim Peyton (Post-doc); Kasie Groom (GA); Lauren Valentino (Americor Intern)
Organization: Hawaii Institute of Marine Biology; University of Hawaii
Grant Number: NA09NOS4260242
Date: 9/1/09 to 8/31/10
II. Executive Summary
Phase shifts on coral reefs have been reported with increasing frequency worldwide over the past 40 years. These benthic communities shifted to unusually low levels of both coral and turf algae cover coincident with a persistent dominance of macroalgae. On Hawaiian reefs this problem has been exacerbated further by introduced macroalgae. These invasive species have replaced not only coral and turf algae but also native seaweeds, such that the benthic cover of some Hawaiian reefs is dominated by species unknown in the islands <60 years ago. The green alga Avrainvillea amadelpha (Bryopsidales) is one example of this phenomenon. First reported in 1981, A. amadelpha has become the dominant cover across a wide range of water depths and substrate types. The coral reefs of Kalaeloa, on the Leeward Coast of Oahu, are located close to the first report of this species on Oahu. For about 15 years scientists at the US Fish and Wildlife Service have been observing this area, concerned about the increasing presence of A. amadelpha on the Kalaeloa reefs. This study was undertaken to provide managers with baseline information on A. amadelpha within subtidal, hard bottom communities of Kalaeloa. We took a two-fold approach to understanding the distribution of A. amadelpha. First, we conducted rapid ecological assessments of sites across the area of interest. The results provided a spatial contrast of habitat characteristics for invaded versus non-invaded habitats. Then, we conducted experimental manipulations to test whether grazer assemblages contribute to the distribution of the standing crop of A. amadelpha recorded at Kalaeloa.
III. Purpose
A. Detailed description of the resource management problem(s) to be addressed. This project was requested to address the status of an invasive alga Avrainvillea amadelpha around the coral reefs of Kalaeloa, Oahu. Resource managers have reported that this species has been increasing in coverage around this site over the last 15 years and they requested that we map this species’ distribution and characterize the invasive species in this area.
B. Overarching goal(s) of the project: Characterize the marine habitats around Kalaeloa – Campbell Industrial Park colonized by the invasive alga Avrainvillea amadelpha.
C. Detailed description of the question(s) asked to answer the resource management problem(s)
A. Where is A. amadelpha found around Kalaeloa? Provide GPS data on its distribution as baseline information on this species. Are there any patterns associated with A. amadelpha distribution at Kalaeloa?
B. Is the physical removal of A. amadelpha a management option for this site? Is there any alternative management options to be considered?
C. What habitats have been invaded by A. amadelpha?
D. Because excessive nutrient loads in coastal waters have been linked to algal invasions elsewhere, is there any evidence that nutrient loading is contributing to the invasion of A. amadelpha around Kalaeloa?
E. Is there any evidence of heavy metals accumulation by A. amadelpha around Kalaeloa?
D. Objectives to answer each question.
A. Map the areal extent of the invasive alga Avrainvillea amadelpha along the coastline from Kalaeloa
B. Monitor the fate of open gaps created by the physical removal of invasive algal biomass
C. Quantify and compare water quality inside and outside Avrainvillea amadelpha canopies
D. Quantify stable isotopes accumulated by Avrainvillea amadelpha canopies
E. Quantify and compare C:N:P of Avrainvillea amadelpha canopies
F. Quantify and compare heavy metals accumulated by Avrainvillea amadelpha canopies
G. Organize a workshop for managers to discuss the results and next steps
IV. Approach
A. Map the areal extent of the invasive alga Avrainvillea amadelpha along the coastline from Kalaeloa. Are there any patterns associated with Avrainvillea amadelpha distribution at Kalaeloa?
i. List individuals and organizations actually performing the work: F. Thomas and K. Peyton planned the work; K. Peyton and K. Groom collected data in the subtidal sites; K. Peyton and L. Valentino collected data in the intertidal sites; L. Valentino assisted on the dive boat; K. Peyton analyzed the data.
ii. Material list: photoquad; digital cameras with underwater housings; underwater strobe; chain for estimating habitat heterogeneity index; transect tape; GPS; ruler; collection bags; underwater paper; clipboard; 10 cm2 quadrat
iii. Construction instructions for anything used to accomplish the III(D) objectives: photoquads see Preskitt et al. (2004); habitat heterogeneity index see Risk (1972)
iv. Data collection procedures: To characterize each site the following were recorded:
o For sites sampled by scuba diving, two independent 15 m transects were laid perpendicular to the shore (shore normal)
o Water depth
o Latitude/longitude (GPS unit towed on a surface float)
o Habitat type:
§ Deep reef (along15-20 m escarpment)
§ Pavement near reef <30 m from reef structure
§ Pavement >30 m from reef structure
§ Shallow reef (inshore 6-12 m)
§ Seagrass meadow
o Benthic contour complexity/habitat heterogeneity index = measure of fine-scale habitat heterogeneity (Risk 1972)
o Urchin counts (along 15 x 2 m belt transect measuring urchin density by species)
o Fish species checklist (record species observed)
o Percent cover of functional groups (coral; turf algae: coralline algae; invasive algae; urchins; etc.) was estimated from 6 photoquad images taken at random points along each transect (Preskitt et al. 2004)
o Within the belt transect area the target species, A. amadelpha, was recorded as either present or not observed. Additionally, on the dives this species was observed at the site but not within a belt transect area, it was noted as rare. When A. amadelpha was present within a belt transect area its standing crop was estimated as:
§ Biomass per unit area (blotted wet weight for some samples and dry weight for all samples) collected by hand from a 10 cm2 quadrat (n = 3-5 per transect)
§ In the laboratory biomass per unit area was partitioned as:
· Total host biomass (A. amadelpha)
· Epiphyte biomass (removed by scraping with a glass slide)
· Total host + epiphyte biomass
· Host frond biomass
· Host holdfast biomass
· Percentage of fronds with grazing scars
§ Dry weight was recorded once the samples reached a constant weight after being placed in a drying oven at 60oC (48-72 hours)
§ A. amadelpha canopy height was estimated using a ruler and measuring to the nearest 0.5 cm
v. Data analysis techniques: Coral Point Count; ANOVA
vi. Photos of the research at each stage:
B. Monitor the fate of open gaps created by the physical removal of invasive algal biomass. Is the physical removal of the invasive species an option? Is there an alternative approach?
i. List individuals and organizations actually performing the work: F. Thomas and K. Peyton designed the experiment; K. Peyton and L. Valentino constructed the cages and tethers; K. Peyton, L. Valentino and K. Groom set up the experiments with K. Peyton and K. Groom doing the deployment. K. Peyton analyzed the data.
ii. Construction instructions for anything used to accomplish the III(D) objectives
· Cages were constructed out of plastic coated metal 1.3 cm2 mesh and measured 15 x 9 x 10 cm
· Cable ties were used to seal the cages
· Tethers were constructed out of twisted polypropylene rope
· Cages and tethers were anchored to the substrate using cable ties
iii. Deployment steps
· Collect A. amadelpha ramets from an area with a mature canopy and place in mesh bags
· Rinse ramets in saltwater to remove sediments and dislodge mobile invertebrates
· On land (stable platform), recorded a blotted wet weight for each replicate
· Replicates were randomly assigned to treatments and sites
· Set out all replicates on the same day in two habitats: collection site (=donor site) and coral reef site (= grazers)
· For each habitat A. amadelpha was tethered in caged and uncaged treatments to obtain an estimate of grazing intensity (=difference between the specific growth rates of caged and uncaged)
· Sample size was six
· One preliminary experiment was run to estimate the approximate grazing rate and determine each experiment’s duration
· For the first experiment the duration was 2 days
· Second experiment was conducted as described above with the exception that only the donor site was used
· For the second experiment the duration was 68 days
iv. Data collection procedures
· Alga was blotted and weighed
· Percent change in biomass was calculated for each replicate
v. Data analysis techniques
· Student t-test and ANOVA
vi. Photos from research during each stage (construction, in situ, lab)
C. Quantify and compare water quality inside and outside Avrainvillea amadelpha canopies
i. List individuals and organizations actually performing the work: K. Peyton and K. Groom did the diving. K. Peyton collected samples.
D. Quantify stable isotopes accumulated by Avrainvillea amadelpha canopies
i. List individuals and organizations actually performing the work: F. Thomas and K. Peyton designed the experiment; K. Peyton collected the samples; K. Peyton and L. Valentino processed samples; Popp Lab (SOEST) analyzed samples
ii. Material list:
· Balance
· Drying oven (60 oC)
· Wig-L-Bug amalgamator using stainless steel liners inside threaded screw vials (plastic)
· Scintillation vials
· Desiccator
iii. Data collection procedures
· Samples A. amadelpha were collected from each site and transported in seawater to laboratory
· Because A. amadelpha was not observed at each site, a second macroalga found at all sites, Neomaris vanbosseae, was added to the study. Where both species co-occurred they were collected together.
· Samples were collected in triplicate
· At the lab, all samples of N. vanbosseae were scraped with a glass slide to remove epiphytes
· A. amadelpha was divided in three sample types
o A. amadelpha - new fronds with no visible epiphytes
o Whole plant A. amadelpha – all fronds with epiphytes
o Whole plant A. amadelpha – holdfast
· Rinsed samples in Nanopure water to remove sediments and salts
· Samples were dried to a constant weight at 60 oC
· Weighted on a Mettler Toledo AB204-S balance
· Ground to a fine power in the Wig-L-Bug amalgamator using stainless steel liners
· Sent to Popp Lab for measurement of tissue d15N and d13C using a Carlo Erba NC2500 Elemental Analyzer interfaced to a Delta S via a ThermoFinnigan ConFloll (mass spectrometer)
iv. Data analysis techniques: ANOVA
v. Contact information for companies used to purchase items unique to your project (if applicable): various companies sell Wig-L-Bug amalgamators – use a search engine to find suppliers (i.e. Goggle). The Popp Lab can be contacted at: http://www.soest.hawaii.edu/gg/isotope_biogeochem/aboutourlab.htm
E. Quantify and compare C:N:P of Avrainvillea amadelpha canopies
i. List individuals and organizations actually performing the work: F. Thomas and K. Peyton designed the experiment; K. Peyton and K. Groom did the diving; K. Peyton collected samples; K. Peyton and L. Valentino processed samples; Popp Lab analyzed the samples
ii. Material list:
· Balance
· Drying oven (60 oC)
· Wig-L-Bug amalgamator using stainless steel liners inside threaded screw vials (plastic)
· Scintillation vials
· Desiccator
iii. Data collection procedures:
· Collected samples of A. amadelpha from each site and transport in seawater to laboratory
· Because A. amadelpha was not observed at each site, a second macroalga found at all sites, Neomaris vanbosseae, was added to the study. Where both species co-occurred they were collected together.
· All samples were collected in triplicate
· At the lab all samples of N. vanbosseae were scraped with a glass slide to remove epiphytes
· A. amadelpha was divided in three sample types
o A. amadelpha - new fronds with no visible epiphytes
o Whole plant A. amadelpha – all fronds with epiphytes
o Whole plant A. amadelpha – holdfast
· Samples were rinsed in Nanopure water to remove sediments and salts
· Samples were dried to a constant weight at 60 oC
· Weighted on a Mettler Toledo AB204-S balance
· Ground to a fine power in the Wig-L-Bug amalgamator using stainless steel liners
· Sent to Popp Lab for measurement of tissue N and C using a Carlo Erba NC2500 Elemental Analyzer interfaced to a Delta S via a ThermoFinnigan ConFloll (mass spectrometer)
iv. Data analysis techniques: ANOVA
v. Contact information for companies used to purchase items unique to your project (if applicable): various companies sell Wig-L-Bug amalgamators – use a search engine to find suppliers (i.e. Goggle). The Popp Lab can be contacted at: http://www.soest.hawaii.edu/gg/isotope_biogeochem/aboutourlab.htm
F. Quantify and compare heavy metals accumulated by Avrainvillea amadelpha canopies
i. List individuals and organizations actually performing the work: K. Peyton and K. Groom were the divers; K. Peyton collected samples; K. Peyton processed samples; Centre National de la Recherche Scientifique analyzed the samples.
ii. Material list
· Balance
· Drying oven (60 oC)
· 15 ml conical tissue grinders (VWR)
· 15 ml centrifuge tubes (VWR)
· Desiccator
iii. Data collection procedures
· At each site Neomaris vanbosseae was collected and, when found, A. amadelpha was collected
· Collected samples in triplicate
· Samples were transported in seawater to the laboratory
· Gloves were used when handling samples
· Any epiphytes were removed by scraping the thalli with a glass slide on a plastic cutting board
· For A. amadelpha only new fronds were used
· New fronds were cut from the holdfast using a plastic knife to avoid introducing metals
· Salts and sediments were rinse from samples using filtered seawater
· Labeled 15 ml tube (VWR) were weighed
· Blotted wet weight of sample was recorded
· Dry sample at 60oC for 3-5 days (constant weight)
· Record dry weight of the sample to calculate wet to dry weight ratio
· Use a tissue grinder to homogenize samples
· Cleaned tube grinder in 1 molar acid with a clean water rinse and dry between samples/sites
· Maintain samples in a desiccator
· Samples were shipped in sealed tubes
iv. Data analysis techniques: ANOVA
v. Contact information for companies used to purchase items unique to your project (if applicable): Use 15 ml centrifuge tubes and tissue grinders from VWR International (vwr.com) because they do not introduce metals into the samples.
G. Organize a workshop
i. List individuals and organizations actually performing the work: Kevin Foster (USFWS), F. Thomas and K. Peyton organized the workshop with 24 participates in attendance
V. Results
A. Map the areal extent of the invasive alga Avrainvillea amadelpha along the coastline from Kalaeloa
a. Accomplishments: A total of 66 sites were surveyed in Kalaeloa. Fifty-two of the sites were surveyed using SCUBA within a depth range of 25 to 90 feet. Sites are situated both north and south of the Barbers Point Harbor channel and included 66 transects. Fourteen sites were surveyed in the intertidal area during spring minus tides. Although we were requested to map the distribution of the invasive alga, we took further steps to provide managers with insights on this invasion and its status at Kalaeloa by characterizing sites with that alga as well as site were the alga was rare or not observed.