Growth and recovery after small-scale disturbance of a rapidly-expanding invasive seagrass in St. John, U.S. Virgin Islands

The Tropical Seagrass Halophila stipulacea: Reviewing What We Know From Its Native and Invasive Habitats, Alongside Identifying Knowledge Gaps

“…The regional spread of H. stipulacea in the Caribbean is likely due to a combination of storm-induced redistribution, interisland vessel transit, and near-shore fishing activities (Willette and Ambrose, 2012;Willette et al, 2014). Fragments of H. stipulacea were shown to survive for days in the water column, settle, and take root (Willette et al, 2020). Smulders et al (2017) showed all H. stipulacea fragments tethered above the sediment rooted within 10 days.…”

“…38.8-47.5 42-70 24-56 36-39 36.9-37.9 Aleem, 1980;Coppejans et al, 1992;Price and Coles, 1992;Kenworthy et al, 1993;Malea, 1994;Debrot et al, 2012;Naser, 2014;Georgiou et al, 2016;Anton et al, 2018 Aleem, 1984;Coppejans et al, 1992;Pereg et al, 1994;Kamermans et al, 2002;Naser, 2014;Mejia et al, 2016;Rotini et al, 2017 Robinson, 1973;Mahalingam and Gopinath, 1987;Coppejans et al, 1992;Price and Coles, 1992;Naser, 2014;Shaltout and Omstedt, 2014;Willette et al, 2020; Growth rate (cm day −1 ) 0.16-1.12 2.7 0.35-0.5 0.5-6.7 Wahbeh, 1984;Angel et al, 1995;Marbà et al, 2002;Willette and Ambrose, 2009;Georgiou et al, 2016 Leaf production (mg day −1 ) 0.02-3.51 10.8 Angel et al, 1995;Marbà et al, 2002 Percent cover (%)…”

“…The traits that make H. stipulacea amenable to invasiveness include rapid horizontal growth and leaf turnover rates (Wahbeh, 1984;Willette and Ambrose, 2012), tolerance to a wide range of environmental conditions, including salinity (Oscar et al, 2018), light (Sharon et al, 2009(Sharon et al, , 2011a, and temperatures (Georgiou et al, 2016). This species has the ability to grow from very small fragments (Willette et al, 2020). It is capable of maintaining high-density meadows in both high and relatively low nutrient levels (Beca-Carretero et al, 2020) in different types of sediments (from soft mud to the nutrientlimited carbonate sediments).…”

“…From the perspective of future management efforts in regions where H. stipulacea might become invasive, we do not believe it would be possible to remove newly discovered plants-unless on a very small scale (<10 m 2 ). Due to its rapid clonal growth, prolonged survival as fragments, and its ability to regrow from small fragments (Smulders et al, 2017;Willette et al, 2020), we need to take into account that if H. stipulacea plants are pulled out, tiny fragments can survive and settle in other places. Perhaps, more efforts should be placed on prevention of loss of native seagrasses.…”

Projected Rapid Habitat Expansion of Tropical Seagrass Species in the Mediterranean Sea as Climate Change Progresses

“…While its expansion has been so far slow in the Mediterranean Sea ( Georgiou et al, 2016 ), its colonization has been rapid in the Caribbean Sea (i.e., Smulders et al, 2017 ; reviewed by Winters et al, 2020 ). Recent studies reported that growth rates from the Caribbean Sea are 8–30 times that of the native Red Sea populations ( Azcárate-García et al, 2020 ; Willette et al, 2020 ). Recent studies from the Caribbean Sea have additionally shown that H. stipulacea is physically displacing local Caribbean species, spreading its dominance within invaded habitats and changing the Caribbean’s seagrass landscape ( Willette and Ambrose, 2012 ; Steiner and Willette, 2015 ; reviewed by Winters et al, 2020 ).…”