ABSTRACT
The seagrass Halophila stipulacea is native to the Red Sea. It invaded the Mediterranean over the past century and most of the Caribbean over the last two decades. Understanding the main drivers behind the successful invasiveness of H. stipulacea has become crucial. We performed a comprehensive study including field measurements, a mesocosm experiment, and a literature review to identify 'superior growth traits' that can potentially explain the success story of H. stipulacea. We assessed meadow characteristics and plant traits of three invasive H. stipulacea populations growing off the Island of Sint Eustatius (eastern Caribbean). We compared similar parameters between native (Eilat, northern Red Sea) and invasive (Caribbean) H. stipulacea plants in a common-garden mesocosm. Lastly, we compared our field measurements with published data. The newly arrived H. stipulacea plants from St. Eustatius were characterized by higher percent cover, higher below- and above-ground biomasses, more apical shoots, and faster leaf turnover rates than those measured in both native and older invaded habitats. These results were further confirmed by the mesocosm experiment where the invasive H. stipulacea plants grew faster and developed more apical shoots than the native plants. Results suggest that increased growth vigour is one of the main invasive traits that characterize successful invasive H. stipulacea populations in the Caribbean and potentially in other invaded areas. We encourage long-term monitoring of H. stipulacea in both native and invaded habitats to better understand the future spread of this species and its impacts on communities and their ecosystem functions and services. Supplementary Information: The online version contains supplementary material available at 10.1007/s10530-023-03045-z.
ABSTRACT
Copper (Cu) is a common marine pollutant of coastal environments and can cause severe impacts on coral organisms. To date, only a few studies assessed the effects of Cu contamination in combination with elevated seawater temperatures on corals. Furthermore, experiments focusing on coral recovery during a depuration phase, and under thermal stress, are lacking. The present study investigated the physiological response of the common and thermally tolerant scleractinian coral Stylophora pistillata from the northern Red Sea to Cu contamination (2.5, 5 or 10 µg L - 1) in combination with thermal stress (5 °C above local ambient temperatures (26 °C)) for 23 days, and assessed the impact of elevated temperatures on its ability to recover from such pollution during a one-week depuration period. Variation in coral photo-physiological biomarkers including antioxidant defense capacity, were dose, time and temperature-dependent, and revealed additive effects of elevated temperatures. Successful recovery was achieved in ambient temperature only and was mediated by antioxidant defenses. Elevation of temperature altered the recovery dynamics during depuration, causing reduced Cu bioaccumulation and photosynthetic yield. The present study provides novel information on the effects of elevated temperature on the resilience (resistance and recovery processes) of a scleractinian coral exposed to a common marine pollutant. Our findings suggest that ocean warming may alter the resilience strategies of corals when exposed to local pollution, an impact that might have long-term consequences on the chances of survival of reefs in increasingly populated and warming coastal environments.
