Spatial and temporal variation of kelp forests and associated macroalgal assemblages along the Portuguese coast

Abstract

Kelp communities are in decline in many regions. Detecting and addressing population declines require knowledge of patterns of spatial and temporal variation in the distribution and abundance of kelps and their associated organisms. We quantified kelp and associated macroalgal assemblages three times over a period of 2 years, at three regions along a natural gradient in temperature and nutrient availability across the Portuguese coast. Kelps were mostly found at the northern cool region (Viana do Castelo), which was also clearly separated from the two more southerly regions (Peniche, Sines) in terms of algal assemblage structure. This pattern was consistent, although varying in intensity, through time, providing support for this general spatial configuration. The overall richness of taxa increased towards lower latitudes. These findings indicated that kelp beds in southern Europe are currently restricted to northern Portugal, though supporting less diverse macroalgal assemblages compared with those located in central and southern Portugal.

Herbivory drives kelp recruits into ‘hiding’ in a warm ocean climate

“…2°), an abrupt macroecological change in the diversity and structure of shallow-water subtidal assemblages was recently reported between central and northern Portugal (Tuya et al 2012, Pinho et al 2015. This is, to some extent, supported by the findings of this study, even though it was not specifically aimed at addressing such issues.…”

“…The regional differences in herbivory on kelp recruits demonstrated in this study matches the inverse pattern of abundance of adult kelps across con tinental Portugal (Tuya et al 2012, Pinho et al 2015. Previously, the presence and fitness of kelps across southern European waters had been exclu-sively linked to bottom-up and climatic influences (Lüning 1990, Bartsch et al 2008, Fernández 2011.…”

“…Northern Portugal is distinct, in terms of reef kelp coverage (> 50%) compared to central Portugal, where kelps are very sparse (Tuya et al 2012, Pinho et al 2015. Water temperatures considered lethal for the focal kelp species (Bartsch et al 2008) are not reached in the studied region (see, for instance, SST data reported for northern and south-western Portugal by .…”

Modulation of different kelp life stages by herbivory: compensatory growth versus population decimation

“…Macroalgal assemblages in the study region include perennial kelp species, which were once abundant and now show a sparse distribution, such as Laminaria ochroleuca, or annual species, such as Phyllariopsis sp. (Assis et al 2009;Tuya et al 2012;Pinho et al 2015). To the abiotic characterization of the study area a set of data loggers were deployed throughout the course of the experiment to measure sea water temperature (ºC) and illuminance (Lux) (HOBO data-loggers Pendant Temp-Light, Onset Computer Corporation), and water movement (m s -2 ) using gravitational data loggers (HOBO Pendant G, Onset Computer Corporation), following (Bennett et al 2015b).…”

Celebrating 25 years of temperate reef science

“…South et al (2016) tested Undaria's effects on the structure and productivity of rocky intertidal assemblages in New Zealand but found few overall effects, presumably because the abundance and distribution of Undaria was highly variable throughout the year. In contrast, Pinho et al (2016) examined kelp communities in three regions in Portugal and found these to be consistent through time.…”