• Invasive species cost the U.S an estimated $120 Billion per year. 1
• The state defines an invasive species as any organism that is “harmful to the environment, economy and/or human health and not native to Hawaii”2
• Invasive macroalgae negatively affect marine areas by monopolizing space, altering geochemistry, and changing food webs.
• Hawai‘i has an estimated 19 species of invasive macroalgae introduced since the 1950’s.3 The main invasive macroalgae in the study area are Gracilaria salicornia (gorilla ogo), Avrainvillea amadelpha (leather mudweed), and Acanthophora spicifera (prickly seaweed).4
• The most common native macroalgae in the channel is Spyridia Filamentosa followed by Wrangelia spp..
• Macroalgae reproduce sexually and asexually through fragmentation.4
• Division of Forestry and Wildlife (DOFAW) manages Paikō Lagoon State Wildlife Sanctuary by improving the aquatic and terrestrial environment through volunteer engagement.
• DOFAW expressed a need for official cost and time effective protocols to manage invasive macroalgae for Paikō Lagoon.
• Objective I: Develop protocols for volunteer-based invasive macroalgae removal and monitoring programs following the constraints of a state agency.
• Objective 2: Evaluate the effectiveness of the developed protocol by monitoring and documenting abundance trends in invasive macroalgae, native macroalgae, and seagrass using the protocols.
• Protocols were based on the Lindenmayer and Liken adaptive management framework7 and incorporated DOFAW constraints, solutions to the current process, literature reviews and experiences in other removal programs.
• The protocols must function on low costs and limited staff, have a task complexity appropriate for middle school students and up, and accommodate volunteer labor, staff availability and tide variations.
• Removal Protocols: Volunteers are introduced to the place and given explanations of the different macroalgae types with a touch tank. Volunteers form groups of four with a set formation and roles to reduce fragmentation and focus on one subsection in a transect. Volunteers remove invasive macroalgae only, placing native macroalgae back into the water and the invasive into buckets that are emptied by staff/chaperones onto the inside of the peninsula.
• Monitoring Protocols: Volunteers form groups of two and record percent cover of 12 evenly spaced quadrats along the inland side of the transects. DOFAW staff then uploads the total coverage of invasive and native macroalgae into an excel driven database.
Paikō Lagoon State Wildlife Sanctuary study area with subsections and transects. Mean percent cover of three categories over 10-month trial period.
|•Invasive macroalgae declined from 45%(95% CI [±11.30]) to 18%(95% CI [±6.28])|
|•Native macroalgae declined from 21% (95% CI [±6.37]) to 1% (95% CI [±.75])|
|•Seagrass had no significant changes.|
Volunteer formation used in removal protocols.
In this trial period, seven removal and four monitoring events reached 287 members of the community with groups from organizations such as Kamehameha Schools, University of Hawai’i at Mānoa, and Kaiser High School.
This project achieved objectives I, to develop removal and monitoring protocols within the constraints of a state agency. This project also addressed objective II, affirming that the protocols are effective at reducing invasive macroalgae but the long-term impacts to native macroalgae require further study.
The native macroalgae decline could be due to seasonality as studies on the main native, Spyridia Filamentosa, show reduced growth at cooler temperatures and the average monthly temperature in the trial period dropped from 80 °F to 74 °F 6. Alternatively, native macroalgae may have floated out of the monitoring area as volunteers separated epiphytic native macroalgae from invasive and returned the native to the water during removal events.
Percent cover data collected during the four monitoring events from June 2017 to March 2018 provide insights into general trends and allow managers to focus efforts on areas with the highest invasive macroalgae coverage.
1. Pimentel, D., Zuniga, R. & Morrison, D. Update on the environmental and economic costs associated with alien-invasive species in the United States. Ecol. Econ. 52, 273–288(2005).
2. Shluker, A. D. State of Hawai‘i Aquatic Invasive Species Management Plan. (2003).
3. Maunalua, M. Maunalua Bay Conservation Action Plan. (2009).
4. Smith, J. E., Hunter, C. L. & Smith, C. M. Distribution and reproductive characteristics of nonindigenous and invasive marine algae in the Hawaiian Islands. Pacific Sci. 56, 299–315 (2002).
5. Conklin, K. Y. Restoration of a Seagrass Bed in Hawai‘i: Understanding the Phytogeography of the Native Red Alga, Spyridia Filamentosa, and its Role in Seagrass Bed Succession. (University of Hawai’i, 2009).
6. Ramírez, R. N. A., Valdez, M. C., García, S. O., López, R. A. N. & Ayala, M. B. C. Spatial and seasonal variation of macroalgal biomass in Laguna Ojo de Liebre, Baja California Sur, Mexico. Hydrobiologia 501, 207–214 (2003).
7. Lindenmayer, D. B. & Likens, G. E. Adaptive monitoring: a new paradigm for long-term research and monitoring. Trends Ecol. Evol. 24, 482–486 (2009).