At present, environmental impacts from offshore oil and gas activities are partly determined by measuring changes in macrofauna diversity. Morphological identification of macrofauna is time-consuming, expensive and dependent on taxonomic expertise. In this study, we evaluated the applicability of using foraminiferal-specific metabarcoding for routine monitoring. Sediment samples were collected along distance gradients from two oil platforms off Taranaki (New Zealand) and their physico-chemical properties, foraminiferal environmental DNA/RNA, and macrofaunal composition analyzed. Macrofaunal and foraminiferal assemblages showed similar shifts along impact gradients, but responded differently to environmental perturbations. Macrofauna were affected by hypoxia, whereas sediment grain size appeared to drive shifts in foraminifera. We identified eight foraminiferal molecular operational taxonomic units that have potential to be used as bioindicator taxa. Our results show that metabarcoding represents an effective tool for assessing foraminiferal communities near offshore oil and gas platforms, and that it can be used to complement current monitoring techniques.

Current climate change scenarios predict that aquatic systems will experience increases in temperature, thermal stratification, water column stability and in some regions, greater precipitation. These factors have been associated with promoting cyanobacterial blooms. However, limited data exist on how cyanobacterial composition and toxin production will be affected. Using a shallow eutrophic lake, we investigated how precipitation intensity and extended droughts influenced: (i) physical and chemical conditions, (ii) cyanobacterial community succession, and (iii) toxin production by Microcystis. Moderate levels of nitrate related to intermittent high rainfall during the summer of 2013-2014, lead to the dominance of Aphanizomenon gracile and Dolichospermum crassum (without heterocytes). Microcystis aeruginosa blooms occurred when ammonium concentrations and water temperature increased, and total nitrogen:total phosphorus ratios were low. In contrast, an extended drought (2014-2015 summer) resulted in prolonged stratification, increased dissolved reactive phosphorus, and low dissolved inorganic nitrogen concentrations. All A. gracile and D. crassum filaments contained heterocytes, M. aeruginosa density remained low, and the picocyanobacteria Aphanocapsa was abundant. A positive relationship (P \ 0.001) was identified between microcystin quotas and surface water temperature. These results highlight the complex successional interplay of cyanobacteria species and demonstrated the importance of climate through its effect on nutrient concentrations, water temperature, and stratification.

Proliferations of the benthic anatoxin-producing cyanobacterium Phormidium are increasing in prevalence in cobble-bed rivers worldwide. This proliferation is of particular concern when rivers are used as sources of drinking water or for recreation. Little is known about the physicochemical variables promoting proliferations, and our existing knowledge is based on data from only a few rivers. We assessed Phormidium cover, physicochemical variables, and anatoxin concentrations at 10 sites in 7 New Zealand rivers every week for 2 y. Generalized additive mixed models (GAMMs) identified dissolved inorganic N (DIN) over the accrual period <0.8 mg/L, dissolved reactive P accrual <0.005 mg/L, water temperatures >157C, and conductivity as having positive and statistically significant effects on % Phormidium cover. Flow intensity, expressed relative to the long-term median, had a positive effect up to 0.4Â the median flow and a negative effect when >0.5Â the median flow. Quantile regression models showed marked variability among sites in relation to the flow intensity required to reduce % Phormidium cover (90 th percentile ranged 0.65-249Â the long-term median flow). Anatoxins were detected in variable concentrations in samples from 7 of the 10 sites. GAMMs identified strong relationships between elevated toxin concentrations and low conductivity and increasing % Phormidium cover, and significantly lower toxin concentrations when DIN was <0.2 mg/L. These data demonstrate that multiple physicochemical variables influence Phormidium proliferations and toxin concentrations and indicate that the relative importance of these variables differs among rivers and sites.

Anthropogenic activity has greatly enhanced the inputs of nitrogen (N) and phosphorus (P) to lakes, causing widespread eutrophication. Algal or cyanobacterial blooms are among the most severe consequences of eutrophication, impacting aquatic food webs and humans that rely on lakes for ecosystem services. In New Zealand, recent debate on the relative importance of N versus P control for limiting occurrences of algal blooms has centered on the iconic Lake Rotorua (North Island). Water quality in Lake Rotorua has declined since the late 1800s following catchment vegetation clearing and subsequent land-use intensification, as well as from sewage inputs. A multimillion dollar restoration programme began in the early 2000s, with key mitigation actions including nutrient load targets for the entire catchment and alum dosing in 2 tributaries. In this manuscript we analyse 2 water quality datasets (>10 yr) from Lake Rotorua and compare these with a global lake dataset. Generalised additive models predicted highly significant (p < 0.001) declines in total phosphorus (TP), total nitrogen (TN) and chlorophyll a (Chl-a) in surface waters between 2001 and 2015. Alum dosing had a negative (i.e., reducing) and highly significant effect on TP and Chl-a (p < 0.001). Correlations of Chl-a on TP and TN were highly significant, but the difference between the 2 correlation coefficients was not, indicating a need to control both nutrients to reduce algal productivity. This conclusion is reinforced by recent bioassay studies which show co-limitation by N and P. Collectively, our data and previous studies provide strong support for the current strategy of limiting both N and P loads to Lake Rotorua for effective eutrophication control.

The global spread of invasive fouling species poses a significant barrier to the development of shellfish aquaculture, which has led to a need to understand the biological characteristics of fouling species that underpin management. One such fouling species, the colonial ascidian Didemnum vexillum, has become a very successful invader in temperate marine communities worldwide, and is proving problematic in a number of aquaculture regions. To evaluate the scope for managing risks to shellfish aquaculture around seasonal reproductive patterns, we assessed recruitment and larval development of D. vexillum in relation to water temperature, over a 20 mo period at 2 locations in central New Zealand. Our findings indicate that the reproductive season for D. vexillum in New Zealand is considerably longer than comparable northern-hemisphere populations (at least 9 mo of the year compared with 3 to 5 mo in the USA). Reproductive patterns were strongly correlated with water temperature, with a 3 mo period during the winter months (surface water temperature <12°C) when larval recruitment was not detected at our study sites. However, during that period, late-stage larvae were often present in tissue sections, suggesting that the species has the potential to recruit year-round, albeit at very low levels during winter. Information on the duration of the reproductive season as well as critical temperature thresholds for spawning will enable more effective risk management in relation to aquaculture industry practices (e.g. timing of seed-stock deployment), as well as assist in the wider management of this species.

No abstract

No abstract

Sedimentation, nutrients and metal loading to coastal environments are increasing, associated with urbanization and global warming, hence there is a growing need to predict ecological responses to such change. Using a regression technique we predicted how maximum abundance of 20 macrobenthic taxa and 22 functional traits separately and interactively responded to these key stressors. The abundance of most taxa declined in response to sedimentation and metal loading while a unimodal response was often associated with nutrient loading. Optimum abundances for both taxa and traits occurred at relatively low stressor levels, highlighting the vulnerability of estuaries to increasing stressor loads. Individual taxa were more susceptible to stress than traits, suggesting that functional traits may be less sensitive for detecting changes in ecosystem health. Multiplicative effects were more common than additive interactions. The observed sensitivity of most taxa to increasing sedimentation and metal loading and the documented interaction effects between multiple stressors have important implications for understanding and managing the ecological consequences of eutrophication, sedimentation and contaminants on coastal ecosystems.