Present-Day Distribution and Potential Spread of the Invasive Green Alga Avrainvillea amadelpha Around the Main Hawaiian Islands

Abstract

Algal assemblages are critical components of marine ecosystems from the intertidal to mesophotic depths; they act as primary producers, nutrient cyclers, and substrate providers. Coral reef ecosystems can be disrupted by stressors such as storm events, effluent inundation, sudden temperature shifts, and non-native invaders. Avrainvillea amadelpha is an invasive green alga that was first recorded in the main Hawaiian Islands on the west shore of Oahu and has continued to be of concern due to its extreme competitiveness with native algae and seagrasses. It has spread rapidly across the island of Oahu, decreasing the biodiversity of the benthos from shorelines to ∼90 m depth. We employed a boosted regression tree modeling framework to identify highly vulnerable regions prone to invasion. Our model indicated that regions exposed to minimal bottom currents and at least five degree heating weeks are particularly susceptible to A. amadelpha colonization. Additionally, we extrapolated our model to the main Hawaiian Islands and forecasted how a 25% increase in statewide annual maximum degree heating weeks may change habitat suitability for A. amadelpha. Across all islands, we identified particularly vulnerable "hotspot" regions of concern for resource managers and conservationists. This manuscript demonstrates the utility of this approach for identifying priority regions for invasive species management in the face of a changing climate.

Predicted Shifts in the Distributions of Atlantic Reef-Building Corals in the Face of Climate Change

“…Each species was modeled individually using two machine learning algorithms and two regression algorithms: random forests (RFs, machine learning; Breiman, 2001), boosted regression trees (BRTs, machine learning; Elith et al, 2008), generalized linear models (GLMs, regression;McCullagh, 1984) and generalized additive models (GAMs, regression;Hastie and Tibshirani, 2014). All these algorithms showed good performances when modeling niches or species distributions in past similar applications (e.g., Chefaoui et al, 2017;Veazey et al, 2019;Morato et al, 2020) and are available on the "BIOMOD2" framework. Readers are referred to the cited original descriptions for more information about each algorithm.…”

Protocol to control the invasive alga Avrainvillea lacerata in a shallow Hawaiian reef flat

“…It is likely that an increase in water flow will cause greater dilution of the oxidant and thus make the reaction time shorter. However, it is suggested that the regions exposed to minimal bottom currents are most susceptible to invasion (Veazey et al, 2019).…”

Taxonomic determination of the cryptogenic red alga, Chondria tumulosa sp. nov., (Rhodomelaceae, Rhodophyta) from Papahānaumokuākea Marine National Monument, Hawai‘i, USA: A new species displaying invasive characteristics

“…A . lacerata has now spread into shallow waters in recent decades from deeper habitats [ 2 , 5 , 6 , 7 ]. More recently, Avrainvillea erecta (Berkeley) A.Gepp & E.S.Gepp has been recorded on O‘ahu and Maui as an introduced species, and continues to rapidly increase in abundance and distribution [ 6 ].…”

“…The origins of the Hawaiian populations of the green alga, A. lacerata, are unknown; some possibilities include that the alga is an indigenous member to the flora or an early introduction before collections of even shallow water algae were first made in about 1826 [4]. A. lacerata has now spread into shallow waters in recent decades from deeper habitats [2,5,6,7]. More recently, Avrainvillea erecta (Berkeley) A.Gepp & E.S.Gepp has been recorded on O'ahu and Maui as an introduced species, and continues to rapidly increase in abundance and distribution [6].…”