Project Description Rationale and Relevance  Purpose and Objectives Methods

PROJECT DESCRIPTION

Rationale and Relevance to HCRI Priorities

• Phase Shifts and Invasive Algal Species
• Intrinsic Factors Controlling Algal Dominance
• Extrinsic Factors Controlling Algal Dominance

Purpose and Objectives

Approach and Methods

• Ecological Surveys of Alien Algae
• Bishop Museum Database and Website
• Growth Parameters of Alien Algae
• Reproductive Strategies of Alien Algae
• Grazing Preferences of Herbivores

Current and Pending Support

Faciliites, Equipment and other Resources

Data Management and Dissemination of Results

Workplan

Anticipated Outcomes and Relevance to Coral Reef Resource

And Management Capabilities

Literature Cited

RATIONALE AND RELEVANCE TO HCRI PRIORITIES

Management strategies for maintaining the health and productivity of coral reefs require a solid basis to support development and assessment of effective action strategies. Alien algal invasions and overfishing (for food and aquarium trade) have been identified as current and significant threats to nearshore reefs in Hawaii. However, we lack even the most basic understanding of the ecological correlates of the success of these pest algae. In Year 1 of HCRI funding, our research focused on the fine-scale interactions among corals, fish grazers and the benthic algae community on Hawaiian reefs. We propose to continue and expand this research in support of management objectives to determine the distribution of alien and invasive algal species throughout the state and to define the intrinsic (growth parameters, reproductive strategies) and extrinsic (nutrient regimes and herbivore grazing pressures) factors controlling their abundance.

• Phase Shifts and Invasive Algal Species

Healthy coral reef ecosystems are typically dominated by reef building corals and coralline algae, with macroalgae and algal turfs generally restricted to those areas of reefs that are relatively less accessible to herbivores. On reefs subject to anthropogenic disturbances such as nutrification or the removal of grazers, macroalgae and turf growth may exceed grazing rates and outcompete corals and coralline algae for space (Littler and Littler 1984, Steneck 1997). The long-term consequences of the resultant phase shifts from coral to invasive algal dominance include loss of productivity and biodiversity, a decrease in the intrinsic value of the reef, changes in the community structure of reef fishes dependent upon corals and algae, and ultimate erosion of the physical structure of the reef (Hughes 1992).

Phase shifts have been documented in Hawaii, with the problem further exacerbated by a number of relatively recent introductions of alien algal species (Table 1). Several of these species have been highly successful (Russell 1987, 1992, Schenkman 1989, Rodgers and Cox 1998) and may be contributing either directly or indirectly to phase shifts from coral to algal domination. Native species of algae also have the potential to become "invasive", leading to massive blooms and coral overgrowth as occurred with Dictyosphaeria cavernosa in Kane’ohe Bay (Smith et al. 1981, Hunter and Evans 1995, Stimson et al. 1996), Cladophora sericea on Maui (Hodgson 1994) and Turbinaria ornata in Tahiti (Peyri 1999, pers. comm.).

Nineteen species of macroalgae have been introduced to Oahu, Hawaii since 1950 (Doty 1961, Brostoff 1989, Russell 987) with at least four of these species being highly successful (Table 1). Some of these nonnative species appear to have spread throughout all of the main Hawaiian Islands, while others are only found on Oahu. Similarly some islands seem to be particularly susceptible to invasion while others appear immune. For example, despite the large blooms of the alien red alga Hypnea musciformis on west Maui, the islands of nearby Kaho’olawe and Molokini are not currently impacted by any species of alien algae (Smith 1998, Smith in prep.). Several alien algal species were brought to Hawaii from Florida or the Philippines in the 1970’s for commercial aquaculture projects that were later abandoned (Russell 1992). Other alien plants were first noted in or around harbors, suggesting that the most likely vector of their transport was through ship fouling and/or ballast water. However, we have scarce current quantitative or even qualitative data on the current distributions of these plants throughout the Hawaiian Islands or on their modes of reproduction and dispersal.

Table 1. Macroalgae introduced to O’ahu since 1950 (after Russell 1992).

The issue of invasive/alien macroalgae phase shifts becomes even more complex when other anthropogenic stresses are imposed on ecosystems. Overfishing and eutrophication, both of which favor algal growth, have lead to drastic and perhaps permanent changes in reef community structure (Kinsey and Davies 1979, Borowitzka 1981, Hatcher and Larkum 1983, Steven and Larkum 1993, Maragos et al. 1996, McClanahan 1997). The intensity of fishing on most coral reefs near human populations is high and alters the standing stock and species composition of fish communities. Marine preserves have been demonstrated to allow fish communities to recover from the impacts of overfishing and reestablish natural population densities to a point where herbivore populations may again control algal distributions (Roberts 1997).

• Intrinsic Factors Controlling Algal Dominance

Ecological factors leading to the success of invasive algal species remain largely unknown. High growth rates, high spore production, effective vegetative propagation, successful epiphytisim, and morphological plasticity all contribute to the ecological success of Hypnea musciformis and Acanthophora spicifera (Rao 1992, Russell 1992). Given the ecologically competitive qualities of these plants, diverse strategies in nutrient acquisition may give them an even greater competitive advantage over native species. In fact, specific areas around the state of Hawaii that are most heavily impacted by these introductions are areas that have been tied to eutrophication events in the past--Kaneohe Bay (Smith et al. 1981) and West Maui (Hodgson 1994, Hodges 1997). The ability to reproduce (sexually or asexually), grow, and utilize various forms of essential nutrients more efficiently than their native counterparts may give a competitive edge to the invasive and/or introduced species.

• Extrinsic Factors Controlling Algal Dominance

In addition to intrinsic factors that contribute to their ecological success, invasive and alien algal species in Hawaii may grow and propagate readily because they are released from natural predators or subjected to a lower abundance of herbivorous grazers. An obvious question is whether herbivore abundance in Hawaii is sufficient, at least in fisheries management areas, to control the spread of invasive algal species. Numbers of major target species for the aquarium fish trade, predominantly herbivores, were significantly reduced in collecting areas relative to control sites on West Hawaii reefs (Tissot and Hallacher in prep.). Therefore, the consequences of aquarium fish collection may also favor algal growth and abundance and we should expect to see a change in reef areas where collecting is now restricted.

Purpose and Objectives

The proposed research seeks to a) document the present distribution and relative abundance of alien and/or invasive algae throughout the main Hawaiian Islands, within and outside of fisheries management areas, including Fish Replenishment Areas (FRAs) b) determine growth, nutrient uptake, and reproductive characteristics of dominant alien algal species, c) assess which, if any, common reef grazers consume alien algae as a food source as well as rates at which such consumption may occur, d) assess the natural grazing rates of major herbivores on Hawaiian reefs, particularly those most heavily impacted by collection for the aquarium trade.

Approach and Methods

The relevant species of algae that will be addressed in this study are presented in Table 1. Prior to conducting field surveys, the database at the Bishop Museum will be accessed and searched in order to tabulate preexisting information from voucher specimens of these plants collected around the state. This will provide us with a historical record and an essential starting point from which to monitor of the distribution and spread of these species. We can then attempt to determine routes of dispersal throughout the islands.

In order to map out the current distribution and/or appearance of alien species of macroalgae in Hawaii, biannual baseline surveys will be conducted at numerous sites around each island, including those identified as "hotspots" by the Department of Aquatic Resources, around the islands of Hawaii, Maui, Molokai, Oahu and Kauai. Alien and/or invasive algal abundance will be ranked on a scale of 0 to 10 (0=0% cover, 10=100% cover) and will include habitat type (e.g.. sand, lava bench, coral, rock, artificial substrate) and pertinent environmental correlates (e.g. depth, proximity to shore) at each site where invasive species are encountered. Sites where alien species presence has been documented in the past will be also be resurveyed. Surveys will be supported by photographic documentation and voucher specimens will be collected and deposited at the Bishop Museum for future reference

Alien species distributions will be plotted on Hawaii GIS bathymetric maps of each of the islands, highlighting depth and habitat type where each alga was found. Maps generated between the biannual surveys will then be compared to determine if there are any substantial differences in abundance attributable to seasonality factors. These maps will also be compared with those generated from the historical data compiled from the Bishop Museum’s database. This will allow us to begin assimilating information that will help to identify sites that may be particularly vulnerable to invasion. Maps will be available on the alien/invasive species web site (http://www.botany.hawaii.edu/invasive) as interactive GIFF files.

Survey sites will be determined in conjunction with DAR representatives on each island. Some sites may be large (ie. Kane’ohe Bay) and will therefore have many smaller subsites embedded within them. We propose to survey thirty or more sites per island. Selected sites will be visited twice a year on each island to account for seasonal variation. Where possible, sites not accessible from shore will be visited via DAR/Botany Dept./Waikiki Aquarium boat support. Surveys will be conducted by snorkeling or using SCUBA when necessary. Video footage and/or underwater photographs will be taken to document the extent of algal dominance at each site.

A workshop will be held in conjunction with I.A. Abbott and C.M. Smith to train HCRI and DAR divers on the identification and field ecology of alien algae. Staff, students, and volunteers from the University of Hawaii’s Marine Option Program will also be trained in alien species identification and will participate in the surveys on all islands. The University of Hawaii’s Diving Safety Officer (David Pence) has also volunteered the use of the divers enrolled in the Scientific Diving class, Spring 2000 to help in conducting SCUBA surveys on the island of Oahu. A web site highlighting alien/invasive algae in Hawaii has been established (http://www.botany.hawaii.edu/invasive) and will be updated as needed to provide research results, educational and public service information. Photographs and video footage will also be made available.

Voucher specimens of all alien and/or invasive species encountered on the aforementioned surveys will be identified in conjunction with Abbott and Smith and will be permanently deposited in the Bishop Museum’s phycological collection. All relevant collection information including date, depth, and habitat attributes will be entered into the museum’s current database and will be readily available to managers via the searchable sites already online at the Bishop Museum.

(http://128.171.128.178:591/FMRes/FMPro?-DB=Alga%20Specimens.FP3&-Lay=WebFields&-Token=25&-Format=TableVw.htm&-Error=Err.htm&-Findall).

A web page addressing all aspects of this research will be added to the preexisting alien/invasive web database and will include visual distribution maps and photographs of alien species. The web page will also include a forum where the general public can ask questions about limu (algae) and alien species. Community members and kupuna will be requested to contribute information to the database.

In order to understand how and why alien species are so successful at certain sites around the Hawaiian Islands, specific growth parameters will be determined. The tolerance ranges and physiological responses of these plants to exposure, light, temperature, salinity, and nutrients will allow us to predict their potential success at specific sites (e.g. depth regimes, areas of fresh water input, reefs near particular watersheds) throughout the state.

Controlled experiments will be conducted at the Waikiki Aquarium to determine the response of Hypnea musciformis, Acanthophora spicifera, Kappaphycus sp., Gracilaria salicornia and Avrainvillia amadelpha to elevated levels of nitrogen and phosphorus. Three basic methodologies will be used to evaluate the response of these plants to differing nutrient regimes, as follows: a) stable isotope forms of nitrogen and phosphorus will be used in the enrichment experiments in order to track and determine the amount of each element taken up by the plants and the rates of incorporation, mass spectrophotometry will used for analysis, b) growth rates will be monitored using % weight increase per unit time, and c) enzymatic assays will be used to determine the efficiency of each plant at using different forms of nitrogen (nitrate and ammonium).

Despite the problems that alien and invasive algal species have caused in Hawaiian waters, little is known about their reproductive biology. As such, it is unclear whether populations of alien and invasive species are sexually or asexually reproducing, or both. Studies have suggested that fragmentation may be tied to invasibility for some species. Acanthophora spicifera secondarily invaded another high island (Kaua‘i) within only 2 years after being found in Pearl Harbor (Doty 1962) and now outcompetes many other algae in indigenous habitats (Russell 1992; Kilar & McLachlan 1986). Hypnea musciformis was intentionally introduced for commercial reasons in 1974; when those failed, its release resulted in rapid spread across islands to well acknowledged bloom proportions for coastal Maui by 1988. Alternatively, species such as Avrainvillea amadelpha are relatively new invaders to the Hawaiian waters, and no published studies have addressed the mechanism of their invasion nor the impact of this most recent introduction.

To investigate whether the alien and invasive species are clonal or sexually reproducing, molecular technologies will be applied to survey the populations for evidence of genetic recombination. In so doing, estimates will be available to determine the levels of extant population variation as well as the degree of genetic recombination taking place. Amplified Fragment Length Polymorphisms (AFLP) will be used to identify variation and recombination. This procedure does not require previous genetic knowledge of the organisms being investigated, an important consideration in surveying a wide array of phylogenetically diverse species. AFLP is a new technology recently developed and being used to fingerprint differences among cultivars of agronomic species (Vos et al, 1995). One of us (CWM) has been using this procedure recently to examine variation in Avrainvillea amadelpha populations (unpublished data). This procedure utilizes both PCR technology, for fast and accurate production of genetic markers, and restriction fragment length polymorphisms to identify variation among individuals.

• Grazing Preferences of Herbivores

Of particular concern is whether herbivore abundance in Hawaii is sufficient to control the spread of invasive algal species. Invasive and alien algal species in Hawaii may grow and propagate more readily than normal because they are partially or fully released from predation, either through absence or depletion of predators. Abundances of major target species for the aquarium fish trade, predominantly herbivores, have been significantly reduced in collecting areas relative to control sites on West Hawaii reefs (Tissot and Hallacher in prep.). Removal of one species of fish can affect the abundance and patterns of distribution of ecologically similar fishes (Robertson et al. 1976, Hixon 1980, Larson 1980). In addition, increases in availability of algal turfs due to removals of one species can produce changes in the grazing and foraging behavior of remaining species (Hourigan 1986). Therefore, the consequences of aquarium fish collection may also favor macroalgal growth and abundance. We should expect to see a difference in the benthic structure of reefs between sites where fish collecting is now restricted compared to sites where it is still allowed.

Many species of tropical algae possess both physical and chemical defenses from herbivory (Duffy and Hay 1990, Bolser and Hay 1996, Hay and Kappel 1994, Paul 1997, Hay 1997). Whether introduced algal species may be eaten by native grazers is entirely unknown. The importance of information about algal palatability is clear: if these species have natural predators, then the implementation of fisheries management strategies to allow the reestablishment of herbivore populations may be an effective management tool for controlling their spread; if they do not, other measures will be necessary.

Feeding trials will be conducted at the Waikiki Aquarium to determine if any of the common herbivores, including fish commonly collected for the aquarium trade, will consume alien species of algae, and if so, their potential rates of consumption. The facilities of the Waikiki Aquarium offer unique opportunities to investigate grazing preferences under controlled and easily observable conditions. This information will allow managers to determine if the proliferation and success of specific alien species of algae is due to the absence of predators or, alternatively, the depletion of native herbivores, at a given site.

Fish will be fasted for 24 hours prior to being offered paired samples of food items for a given amount of time. These pairs will consist of an alien alga and a native counterpart. The wet weight of each alga will be determined before and after feeding trials and results will be reported as mean biomass of algal tissue removed. The amount and type of food eaten by each species of fish will be recorded. Information and results will be made available to managers through technical reports and public seminars presented at the Waikiki Aquarium.

In the field, feeding rates by herbivorous acanthurid fishes will be quantified by counting the number of bites taken by focal individuals of common aquarium fish collection (e.g. Zebrasoma flavescens, Ctenochaetus strigosus, and Acanthurus achilles) and non-aquarium trade species (e.g. Acanthurus triostegus and A. nigroris). Final selection of study species will be based upon data collected by HCRI and Hawaii DLNR Division of Aquatic Resources personnel.

Biomass removal by individual grazers will be quantified by allowing individual fish to graze on turf-encrusted tiles. PVC tiles (5 cm x 5 cm) will initially be placed in caged enclosures on the reef for 30 days, allowing development of an algal community in the absence of fish grazing. The wet weight of each tile will be recorded prior to exposure to a selected herbivore. An individual of one of the focal species will be allowed to graze on a tile for a 10-30 minute period. The number of bites taken will be recorded, and the tile will be re-weighed following the bout of grazing. In this way, the amount of biomass removed per bite and per unit time can be determined for each species. Since these bites will be occurring on a rich, previously ungrazed sample of artificial substratum, these rates will likely represent maximum grazing rates for each species.

Biomass removal experiments will be repeated with samples of natural substratum from the reef. Where possible, algae-encrusted pieces of calcareous rubble measuring approximately 4 cm in greatest dimension will be used to minimize the need to physically dislodge pieces of the reef itself. Since these pieces of substratum will have been exposed to normal grazing pressure on their respective reefs, rates of biomass removal calculated from these samples will represent a minimum grazing rate by the focal fish species.

To verify the results of laboratory preferences tests, multispecies preference tests will be conducted in the field at selected sites. In these tests, thalli of several algal species will be weighed, placed in individual holders, and placed on the reef. At the end of a 24 hour time period, they will be retrieved and reweighed, with the weight loss of each species over that time period being a measure of the preference rankings of the herbivore community for those algal species. These multispecies algal arrays will also be observed for 30 minute time periods while in the field, with the number and species of fish feeding on the individual algal species being recorded.

FACILITIES, EQUIPMENT AND OTHER RESOURCES

--UH-Botany--experimental microcosms, algal physiology lab, department vehicle on island of Hawaii

--Waikiki Aquarium--experimental aquariums, access to captive fish, 17' Boston Whaler

--HIMB--experimental microcosms, access to research reserve

--collaboration with local experts, HCRI [CRAMP, FACET], MOP and DAR scientists

DATA MANAGEMENT AND DISSEMINATION OF RESULTS

All data acquired over the course of this study will be public information and shared with managers, researchers, co-workers, students, government agencies, and the general public. The results of this research will be made available to 1) fisheries and coral reef ecosystem managers through reports and recommendations, 2) the scientific community through publications in refereed journals and presentations at local, national, and international meetings, and 3) the general public through press releases and website postings.

WORKPLAN

Table 2. Timeline of tasks and proposed management structure.

Anticipated Outcomes and Relevance to Coral Reef Resource Management

Results of this study will be used to generate distribution maps of alien and invasive algal species throughout the state of Hawaii. This will provide managers with the ability to visualize the extent of current distributions, to monitor rates of expansion and invasion of new areas, and to assess the effectiveness of management actions. Sites heavily impacted by alien/invasive algae, as identified by Hawaii State managers and this study, will be extensively surveyed and compared to control (non-impacted) sites in order to determine specifically how these aliens are affecting native reef ecosystems.

Herbivores play a significant role in controlling the standing crop of algae in any marine ecosystem. We will identify whether natural predators have the potential to control alien/invasive algal abundance on Hawaiian reefs This information will then allow managers to determine if the success of these aliens at any given site is due to a lack of natural predators or whether it may be exacerbated by overfishing. Low palatability to native herbivores may in itself explain blooms of alien algal species. Alternatively, if native herbivores will consume nonnative or invasive algal species, then we can predict that areas where herbivores are depleted will be more susceptible to algal invasions. The development and implementation of fisheries management areas to increase the abundance of herbivores on a reef may then be an effective tool for reducing alien species abundance.

Preference rankings of herbivores for algal species will assist in determining if the proliferation and success of specific alien species of algae is due to the absence of any predator (the invasive is ignored in favor of more preferred food sources) or is the result of the removal or lack of herbivores (overfishing) at a given site. The grazing pressure they experience will be a function of the biomass and species composition of herbivores present, the abundance of algae indigenous to the site, and the preference ranking of the invasive species relative to the indigenous algae. Densities of the focal grazing species (from data collected by us, HCRI-CRAMP, and the Division of Aquatic Resources) will then be combined with grazing rates of individual fish species to estimate potential rates of algal biomass removal in and out of Fish Replenishment areas.

This research will provide much needed information on the distribution, abundance, growth, and reproductive capabilities of pest algae, as well as the potential for their removal by natural grazers. This information will allow managers to more precisely predict the type of habitat that alien and invasive algae are able to invade, as well as conditions in which they are least successful. This fundamental research is crucial to enabling management measures for controlling the populations of alien and invasive algal species and for evaluation of fisheries management options to insure the health of Hawaii's coral reef ecosystems.

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