Volume 58, Issue 2

Nonindigenous marine species continue to be one of the foremost threats to marine biodiversity. As an update to a 2007 review of the impacts of introduced macroalgae, we assessed 142 additional publications to describe species’ impacts as well as to appraise information on the mechanisms of impact. Only 10% of the currently known nonindigenous macroalgal species were subjects of ecological impact studies, with changed community composition as the most commonly reported effect. Economic impacts were rarely published. Recent research has focused on the impacts of introduced macroalgal assemblages: red algal introductions to the Hawaiian Islands and turf algae in the Mediterranean. Several general issues were apparent. First, many publications included nonsignificant results of statistical analyses but did not report associated power. As many of the studies also had low effect and sample size, the potential for type II errors is considerable. Second, there was no widely accepted framework to categorize and compare impacts between studies. Information in this updated review was still too sparse to identify general patterns and mechanisms of impact. This is a critical knowledge gap as rates of introductions and hence impacts of nonindigenous macroalgae are expected to accelerate with climate change and increasing global trade connectivity.

Lessonia nigrescens used to be an abundant kelp species along the Chilean coast, but recent molecular studies revealed the existence of a L. nigrescens species complex, which includes the two cryptic species Lessonia berteroana and Lessonia spicata . Since these species have different distributions (16°S–30°S for L. berteroana and 29°S–42°S for L. spicata ), they experience differences in environmental conditions, such as solar irradiance, seawater temperature and air exposure during low tide. This study tested to what extent the genetic distinctness of each of the two species [identified by a mitochondrial marker ( atp8/trnS )] is reflected by ecophysiological traits (total lipids, fatty acid composition, phlorotannins, pigments and variable chlorophyll a fluorescence of PSII) in response to the respective environmental conditions, prevailing along the latitudinal gradient. We studied algal individuals from eight populations (27°S–32°S, including the species overlapping zone). Phlorotannins, pigments and Chl a fluorescence of PSII were most crucial for species-specific adaptations at the respective growth sites, whereas changes in total lipids and fatty acid compositions were negligible. Hence, species differentiation within the L. nigrescens complex is also manifested at the ecophysiological level. These findings may help to predict kelp responses towards future environmental changes.

Marine coastal ecosystems are suffering from metal pollution such as mercury. Hizikia fusiformis is a commercially important brown marine macroalga. Entire thalli of H. fusiformis were cultured in media with different mercury concentrations for 7 days to examine the physiological effects of mercury exposure on this species. The relative growth rate of H . fusiformis was significantly reduced at 0.04 mg l -1 mercury. Chlorophyll a and carotenoid contents were not affected by mercury concentrations ≤0.10 mg l -1 , but significantly decreased at 0.20 and 0.40 mg l -1 . Optimal quantum yield, maximum net photosynthetic rate, and apparent photosynthetic efficiency were reduced with increasing mercury concentrations. Malondialdehyde contents were significantly increased at 0.04–0.40 mg l -1 mercury. Superoxide dismutase activity increased at 0.02–0.10 mg l -1 mercury. Both superoxide dismutase and catalase activity strongly decreased at 0.20 and 0.40 mg l -1 . Nitrate reductase activity declined at mercury concentrations ≥0.04 mg l -1 . Consequently, the results suggest that H. fusiformis could tolerate mercury stress at very low concentrations but that mercury at high concentrations has toxic effects on H . fusiformis through its negative influence on photosynthesis and related physiology. The results also illuminate the physiological response mechanisms of algae to mercury exposure.

Chondracanthus teedei and C. chamissoi are regarded as cosmopolitan and endemic species, respectively. To verify the geographic distribution of these two species, we analyzed specimens of C. teedei from the Western Pacific and the Atlantic coast of Spain, as well as of C. chamissoi from Chile using plastid rbc L and mitochondrial COI genes. The phylogenetic tree of rbc L revealed that “ C. teedei ” from Asia and Chondracanthus sp. from France are conspecific with C. chamissoi from Chile, but distinct from the clade of C. teedei from the Atlantic. These results indicate that C. chamissoi is not exclusively distributed in the southeastern Pacific, but is also found in Korea/Japan and France, whereas C. teedei is found in the Atlantic and not in the western Pacific region. This study demonstrated that the range of C. chamissoi is wider than previously thought, raising interesting questions regarding the transportation vector and the absence of C. teedei from Korea and Japan. In addition, we confirmed that molecular analyses can be used to examine the geographic distribution of marine macroalgae.

In 2010, we surveyed 42 sampling locations at 11 sites along the Mexican part of the Mesoamerican Reef System, including eight protected natural areas of the coastal state of Quintana Roo, to determine the richness of benthic-epiphytic dinoflagellates in the area. At each site, the host macroalgae of the genera Dictyota , Halimeda , Laurencia , Sargassum , and Stypopodium were manually collected. A total of 383 samples were analyzed microscopically using transmitted light, epifluorescence with calcofluor staining, and scanning electron microscopy. A total of 24 dinoflagellate species distributed among the genera Amphidinium , Bysmatrum , Coolia , Gambierdiscus , Ostreopsis , Prorocentrum , Plagiodinium , and Sinophysis were identified. Prorocentrum is the most diverse genus in the benthic-epiphytic environment with 13 species. This work also includes 15 new records of species from the Mexican Caribbean.

Thraustochytrids, a group of fungus-like organisms belonging to the protist class Labyrinthulomycetes, are common colonisers and degraders of fallen leaves in mangroves and, thus, are actively involved in nutrient cycling. Mangroves, often located at the river mouth, constantly receive freshwater runoff, which contains organic and inorganic pollutants, including metals. Metals are known to cause cellular damage, which may affect the survival of thraustochytrids in the mangrove environment. A previous study suggested that Cu(II), one of the major metal ions in coastal water and sediment, retards the growth of and causes cellular damage to mangrove thraustochytrids. We hypothesize that increased concentrations of Cu(II) negatively affect the fecundity of mangrove thraustochytrids. In a laboratory study, we assessed the sporulation success (number of zoospores produced per colony) and the growth response (biomass) of 11 isolates of Schizochytrium limacinum collected from four mangrove stands in Taiwan exposed to increasing concentrations of Cu(II). Tolerance to Cu(II) varied among the tested isolates of S. limacinum . In general, a negative dose-response relationship was exhibited between growth response/sporulation success and increasing concentrations of Cu(II). However, exposure to low concentrations of Cu(II) had a stimulating effect on growth (2 mg l -1 ) and sporulation (2–64 mg l -1 ) for some isolates. A sharp decline in growth was observed at 32 mg l -1 Cu(II), and sporulation success was more tolerant to increasing concentrations of Cu(II). The IC 10 and IC 50 values for growth were 1.0–16.5 mg l -1 and 9.1–23.9 mg l -1 , respectively, whereas those for sporulation success were 0.6–40.7 mg l -1 and 10.5–108.4 mg l -1 , respectively. In conclusion, Cu(II) interfered with both the growth and sporulation success of S. limacinum , which may affect its abundance and distribution in mangrove environments.