Topographic shading and wave exposure influence morphology and ecophysiology of Ecklonia radiata (C. Agardh 1817) in Fiordland, New Zealand

Abstract

Patterns in morphology, pigment concentration, and light saturation kinetics of Ecklonia radiata reveal great morphological and physiological variability among individuals from sites spanning strong gradients in topographic shading and wave exposure among the 14 fjords in southwestern New Zealand. Morphology of E. radiata varies from relatively narrow (85 6 4.7 mm) (mean 6 standard error), thick (3.2 6 0.30 mm) blades from the well-illuminated, wave-exposed outer coast sites to wide, undulate (460 6 36.8 mm,) and thin (0.46 6 0.059 mm) blades from quiescent, topographically shaded inner fjord sites. Chlorophyll a (Chl a) concentration of blades (0.084-1.34 mg g 21 of tissue) and the ratio of fucoxanthin to Chl a (0.33 to 0.56) also increased along this gradient, indicating photoacclimation within the inner fjord populations. In situ measurements of light saturation kinetics indicate maximum photosynthetic rates at lower irradiance (I max 5 43.7 vs. 257 mmol quanta m 22 s 21 ) for algae at inner fjord sites relative to well-lit outer fjord locations. Individuals exhibiting characteristically photoacclimated relative electron transfer rate curves had more deplete d 13 C (213.35% to 222.35%) than individuals with higher I max . There was no significant association between the kelp morphology or geographic location and the observed recombinant DNA diversity of ITS sequences that would indicate the presence of two Ecklonia species in the fjords. E. radiata occupies a wide range of habitats in Fiordland and displays variability in morphology and photo-physiological responses to low light that coincide with gradients in wave exposure and topographically shaded light conditions.

A safety network against regional population collapse: mature subpopulations in refuges distributed across the landscape

“…Rock wall habitats contain a relatively low diversity of suspension feeding invertebrates with brachiopods and tubeworms as dominant space occupiers (Smith 2001, Wing andJack 2012). There are very low densities of macroalgae, and no significant beds of the common kelp Ecklonia radiata (Wing et al 2007). In this study, Long Sound supported dense populations of blue cod, which have increased since the marine reserve was established.…”

“…Situated in the south west of New Zealand, this system is characterised by strong gradients in environmental conditions, primarily salinity, light and wave exposure, which have a dramatic influence on productivity patterns (Goebel et al 2005, Wing et al 2007, Wing and Leichter 2011. The resultant spatial diversity in basal organic matter sources fuelling food webs can be directly linked to subpopulation structure, growth and fecundity of benthic invertebrates , Jack et al 2009, Wing 2009 and reef fish (Rodgers and Wing 2008, Lawton et al 2010, McLeod et al 2010a).…”

Marine reserve networks conserve biodiversity by stabilizing communities and maintaining food web structure

“…Commonly employed impact-control studies measure spatial management outcomes by comparing regions that are under different management regimes (no-take reserve, commercial exclusion zones, open fished areas) but that are otherwise comparable, before and after implementation. However the New Zealand fjords are characterized by strong physical environmental gradients containing the extremes of salinity, wave action and irradiance that together influence patterns of pelagic productivity and density of habitatproviding macroalgae along the axis of each fjord (Goebel et al 2005, Wing et al 2007). The resulting gradient in composition of organic matter source pools can be directly linked to diet, sub-population structure, growth and fecundity of reef fish (Wing et al 2012, Beer andWing 2013).…”

Morphological variability of intertidal Eisenia arborea (Laminariales, Ochrophyta) at Punta Eugenia, Baja California Sur

“…This was clearly proved in the stipe morphology as we found differences in length and diameter. Similarly, kelps show important phenotypic plasticity in response to environmental heterogeneity, such as waveexposure in Ecklonia radiata (Wernberg et al 2003, Wing et al 2007 is also inversely correlated to water temperatures Kremer 1984, 1986). On the other hand, Hernández-Carmona et al (2001) demonstrated that E. arborea, differing from M. pyrifera, maintained high tissue nitrogen content.…”