Water motion and pH jointly impact the availability of dissolved inorganic carbon to macroalgae.

The supply of dissolved inorganic carbon to seaweeds is a key factor regulating photosynthesis. Thinner diffusive boundary layers at the seaweed surface or greater seawater carbon dioxide (CO) concentrations increase CO supply to the seaweed surface. This may benefit seaweeds by alleviating carbon limitation either via an increased supply of CO that is taken up by passive diffusion, or via the down-regulation of active carbon concentrating mechanisms (CCMs) that enable the utilization of the abundant ion bicarbonate (HCO).

Effect of temperature on sporulation and spore development of giant kelp (Macrocystis pyrifera).

Rising ocean temperature is a major driver of kelp forest decline worldwide and one that threatens to intensify over the coming decades. What is not particularly well understood are the mechanisms that drive loss and how they operate at differing life stages. This study aimed to establish an understanding of the effects of increasing temperature on the early developmental stages of the giant kelp, Macrocystis pyrifera.

Coralline photosynthetic physiology across a steep light gradient.

Coralline algae (CA) are globally distributed and fulfil many important roles within coastal ecosystems. In this study, photosynthetically active radiation (PAR) measured for 616 days at 2 and 10 m in a temperate subtidal kelp forest in southern New Zealand provided context to photosynthesis vs. irradiance relationships for, and pigment concentrations of, an articulated coralline alga, Arthrocardia sp.

Reducing the arbitrary: fuzzy detection of microbial ecotones and ecosystems - focus on the pelagic environment.

Background: One of the central objectives of microbial ecology is to study the distribution of microbial communities and their association with their environments. Biogeographical studies have partitioned the oceans into provinces and regions, but the identification of their boundaries remains challenging, hindering our ability to study transition zones (i.e.

Whole community estimates of macroalgal pigment concentration within two southern New Zealand kelp forests.

Light availability is a fundamental factor that controls the productivity and distribution of macroalgae and is highly variable, both spatially and temporally, in subtidal coastal systems. Our comprehension of how macroalgae respond to such variability is a significant knowledge gap that limits our understanding of how light influences the structure and productivity of these environments. Here, we examined the pigment characteristics of individual species, and for the first time the whole community, within one low-light, and one high-light kelp-forest system in southern New Zealand.

Light dose versus rate of delivery: implications for macroalgal productivity.

The role of how light is delivered over time is an area of macroalgal photosynthesis that has been overlooked but may play a significant role in controlling rates of productivity and the structure and persistence of communities. Here we present data that quantify the relative influence of total quantum dose and delivery rate on the photosynthetic productivity of five ecologically important Phaeophyceae species from southern New Zealand. Results suggested that greater net oxygen production occurs when light is delivered at a lower photon flux density (PFD) over a longer period compared to a greater PFD over a shorter period, given the same total dose.

Restricted use of nitrate and a strong preference for ammonium reflects the nitrogen ecophysiology of a light-limited red alga.

Ammonium and nitrate are important sources of inorganic nitrogen for coastal primary producers. Nitrate has higher energy requirement for uptake and assimilation, compared with ammonium, suggesting that it might be a more efficient nitrogen source for slow-growing, light-limited macroalgae. To address this hypothesis, we examined the nitrogen ecophysiology of Anotrichium crinitum, a rhodophyte macroalgae common in low-light habitats in New Zealand.

Light Limitation within Southern New Zealand Kelp Forest Communities.

Light is the fundamental driver of primary productivity in the marine environment. Reduced light availability has the potential to alter the distribution, community composition, and productivity of key benthic primary producers, potentially reducing habitat and energy provision to coastal food webs. We compared the underwater light environment of macroalgal dominated shallow subtidal rocky reef habitats on a coastline modified by human activities with a coastline of forested catchments.

Predicting invasive species impacts: a community module functional response approach reveals context dependencies.

Predatory functional responses play integral roles in predator-prey dynamics, and their assessment promises greater understanding and prediction of the predatory impacts of invasive species. Other interspecific interactions, however, such as parasitism and higher-order predation, have the potential to modify predator-prey interactions and thus the predictive capability of the comparative functional response approach. We used a four-species community module (higher-order predator; focal native or invasive predators; parasites of focal predators; native prey) to compare the predatory functional responses of native Gammarus duebeni celticus and invasive Gammarus pulex amphipods towards three invertebrate prey species (Asellus aquaticus, Simulium spp.

Turf wars: experimental tests for alternative stable states in a two-phase coastal ecosystem.

Alternative stable states have long been thought to exist in natural communities, but direct evidence for their presence and for the environmental switches that cause them has been scarce. Using a combination of greenhouse and field experiments, we investigated the environmental drivers associated with two distinctive herbaceous communities in coastal ecosystems in New Zealand. In a mosaic unrelated to micro-topography, a community dominated largely by native turf species (notably Leptinella dioica, Samolus repens, and Selliera radicans) alternates with vegetation comprising exotic (i.

Coupled hydrodynamic and wastewater plume models of Belfast Lough, Northern Ireland: a predictive tool for future ecological studies.

Wastewater outfalls provide a natural laboratory for the study of nutrient dynamics in coastal seas, however if properly designed and operated their impact can be difficult to detect. A model was developed and applied to investigate the effect of variation in hydrodynamic conditions on the transport and dilution of a treated wastewater plume in Belfast Lough, Northern Ireland. To validate these predictions we measured the physiochemical properties of the waters surrounding the outfall with a specific focus on inherent plume tracers likely to be relevant to the study of macroalgae (salinity, nitrogen and phosphorus).

Survival in low light: photosynthesis and growth of a red alga in relation to measured in situ irradiance.

Reduced light availability for benthic primary producers as a result of anthropogenic activities may be an important driver of change in coastal seas. However, our knowledge of the minimum light requirements for benthic macroalgae limits our understanding of how these changes may affect primary productivity and the functioning of coastal ecosystems. This knowledge gap is particularly acute in deeper water, where the impacts of increased light attenuation will be most severe.

CARBON-USE STRATEGIES IN MACROALGAE: DIFFERENTIAL RESPONSES TO LOWERED PH AND IMPLICATIONS FOR OCEAN ACIDIFICATION(1).

Ocean acidification (OA) is a reduction in oceanic pH due to increased absorption of anthropogenically produced CO2 . This change alters the seawater concentrations of inorganic carbon species that are utilized by macroalgae for photosynthesis and calcification: CO2 and HCO3 (-) increase; CO3 (2-) decreases. Two common methods of experimentally reducing seawater pH differentially alter other aspects of carbonate chemistry: the addition of CO2 gas mimics changes predicted due to OA, while the addition of HCl results in a comparatively lower [HCO3 (-) ].