Richard B. Taylor

Short-term dynamics of a seaweed epifaunal assemblage

Abstract This paper examines short-term stability and movement patterns of the mobile epifaunal assemblage inhabiting a dense subtidal bed of the fucalean seaweed Carpophyllum plumosum var. capillifolium (A. Richard) Lindauer, in northeastern New Zealand. Four-hourly sampling of plants around the clock during all four lunar phases revealed no clear patterns in the abundance of total animals or of most individual taxa. The only exceptions were cumaceans, mysids and eusirid amphipods, which were more abundant on (or near) the plants at night. Recolonization experiments revealed a night-time turnover of 35–42% of total epifaunal individuals on plants within clumps (i.e. plants in physical contact with other plants). Turnover rates were much lower on clumped plants during the day (8–22%), and on plants isolated in small coralline turf patches during day and night (4–12%). For the major epifaunal groups, night-time turnover on clumped plants was highest for amphipods (55–69% of individuals), followed by isopods (17–60%), and gastropods (11–16%). Together, these results indicate that epifaunal movement was mainly by crawling from plant to plant, rather than by swimming at night as a component of the demersal zooplankton. This contrasts with the findings of some previous studies, where epifauna recolonized isolated plants at higher rates than clumped plants, apparently because isolated plants acted as a sink for epifauna resettling from the water column at dawn. It is suggested that the density of plants within macrophyte beds determines the extent to which epifauna disperse by crawling versus swimming in the water column.

Seasonal variation in assemblages of mobile epifauna inhabiting three subtidal brown seaweeds in northeastern New Zealand

Seasonal variation in densities of mobile epifauna associated with three species of subtidal brown seaweeds (Phaeophyta) was investigated over 2–3 years in northeastern New Zealand. There was strong seasonal variation in the total number of individuals per plant wet weight for epifauna inhabiting two fucalean seaweeds of the genus Carpophyllum, with epifaunal densities roughly tracking solar irradiance. In contrast, epifaunal densities on the laminarian Ecklonia radiata peaked during autumn/winter in the first two years of sampling, and during spring in the third, showing no predictable seasonal pattern of abundance. Few individual epifaunal taxa showed clear seasonal abundance patterns, even on the Carpophyllum spp. The composition of the epifaunal assemblage on each seaweed species was fairly constant over time.

MEASURING RATES OF AMMONIUM ASSIMILATION IN MARINE ALGAE: USE OF THE PROTONOPHORE CARBONYL CYANIDE m‐CHLOROPHENYLHYDRAZONE TO DISTINGUISH BETWEEN UPTAKE AND ASSIMILATION

A method for determining rates of ammonium assimilation in marine algae is described. Ammonium assimilation is defined as the decrease in total (medium + cellular) ammonium. The protonophore carbonyl cyanide m‐chlorophenylhydrazone (CCCP) was used to distinguish between uptake and assimilation of ammonium. Ammonium uptake by nitrogen‐replete and nitrogen‐starved cells of the diatom Phaeodactylum tricornutum Bohlin and the green macroalga Enteromorpha sp. was completely (98%–99%) inhibited in the presence of 100 μM CCCP. In addition to inhibiting further uptake of ammonium, CCCP promoted the release of unassimilated ammonium by nitrogen‐replete and nitrogen‐starved P. tricornutum and Enteromorpha that had been allowed to take up ammonium for a period. Most (97.5%) of preaccumulated 14C‐methylammonium was released by nitrogen‐starved P. tricornutum in the presence of CCCP. Specific rates of ammonium assimilation in nitrogen‐replete cultures of P. tricornutum were identical to the maximum growth rate, but specific rates in nitrogen‐starved cultures were fourfold greater. Rates of ammonium assimilation in Enteromorpha during both the surge and the internally controlled uptake phases were the same as the internally controlled rate of uptake, suggesting that the latter is a reliable measure of the maximum rate of assimilation.

A portable battery-powered suction device for the quantitative sampling of small benthic invertebrates

Abstract An inexpensive battery-powered suction device for quantitative sampling of small mobile invertebrates from shallow water substrata is described. The sampler efficiently collected animals from an articulated coralline algal turf habitat. It is easier to transport and operate in the field than similar existing devices, and has a wide range of potential applications.

Biologically Active Acetylenic Amino Alcohol and N-Hydroxylated 1,2,3,4-Tetrahydro-β-carboline Constituents of the New Zealand Ascidian Pseudodistoma opacum

The first occurrence of an acetylenic 1-amino-2-alcohol, distaminolyne A (1), isolated from the New Zealand ascidian Pseudodistoma opacum, is reported. The isolation and structure elucidation of 1 and assignment of absolute configuration using the exciton coupled circular dichroism technique are described. In addition, a new N-9 hydroxy analogue (2) of the known P. opacum metabolite 7-bromohomotrypargine is also reported. Antimicrobial screening identified modest activity of 1 toward Escherichia coli, Staphylococcus aureus, and Mycobacterim tuberculosis, while 2 exhibited a moderate antimalarial activity (IC50 3.82 μM) toward a chloroquine-resistant strain (FcB1) of Plasmodium falciparum.

Trajectories of spiny lobster Jasus edwardsii recovery in New Zealand marine reserves: is settlement a driver?

DEBBIE J . FREEMAN 1 , 2 ∗, ALISON B . MACDIARMID 3 , RICHARD B . TAYLOR 1 , ROBERT J. D AVIDSON 4 , ROGER V. GRACE 5 , T I M R. H A G G I T T 6 , SHANE KELLY 7 A ND N ICK T . SHE AR S 8 1University of Auckland, Leigh Marine Laboratory, PO Box 349, Warkworth 0941, New Zealand, 2Department of Conservation, PO Box 10-420, Wellington 6143, New Zealand, 3National Institute of Water and Atmospheric Research, PO Box 14-901, Kilbirnie, Wellington 6241, New Zealand, 4Davidson Environmental Ltd, PO Box 958, Nelson 7040, New Zealand, 5Mountains to Sea Conservation Trust, c/o 539 Rockell Road, RD1, Hikurangi, Whangarei 0181, New Zealand, 6Coastal and Aquatic Systems Ltd, PO Box 54, Leigh 0947, New Zealand, 7Coast and Catchment Ltd, 3 The Brae, Maraetai Beach, Manukau City 2018, New Zealand, and 8University of Auckland, Department of Statistics, Private Bag 92019, Auckland 1142, New Zealand Date submitted: 19 July 2011; Date accepted: 10 April 2012

Mussel reefs on soft sediments: a severely reduced but important habitat for macroinvertebrates and fishes in New Zealand

Green-lipped mussels (Perna canaliculus) formed extensive reefs on soft sediments in sheltered embayments around northern New Zealand until overfishing and/or increased sediment input caused their virtual disappearance by 1980. To determine the role of mussel reefs as habitat for other animals, we located remnant soft-sediment reefs in five locations and compared the density, biomass, productivity and composition of mobile macroinvertebrate communities, and the density of small fishes associated with mussels, with fauna in the surrounding soft sediments. The mussel reefs had a distinct assemblage of macroinvertebrates, which had 3.5 times the density, 3.4 times the biomass and 3.5 times the productivity of surrounding areas. The density of small fishes was 13.7 times higher than in surrounding areas. These results show that soft-sediment mussel reefs support an abundant and productive fauna, highlighting the probable large loss of productivity associated with the historical decline in mussel habitat and the consequent desirability of restoration efforts.

Soft‐sediment habitats and fauna of Omaha Bay, northeastern New Zealand

Abstract The aim of this paper is to describe the distribution and abundance of animals living in the subtidal soft‐sediments of Omaha Bay in northeastern New Zealand. Animals >4 mm were sampled from 138 subtidal stations, using suction sampler, grab, and dredge. Stations ranged in depth from 1 to 41 m, with sediments comprised mostly of sand and gravelly sand. Two‐hundred‐and‐thirty‐six taxa representing 13 phyla were recorded, with molluscs, arthropods and annelids being the most speciose. Animals sampled by grab and suction sampler formed seven main clusters in multivariate space. These clusters were relatively discrete in terms of the defining variables used to label them and the taxonomic composition of the animals they contained, although depth ranges of most common taxa in the four sand habitats did not correspond particularly well to breaks identified by the cluster analysis. The overall correspondence between the macrofaunal assemblages and the physical variables of depth and sediment type suggests the potential for remote mapping of these broad assemblages over large scales using existing acoustic survey methods.

Predators indirectly induce stronger prey through a trophic cascade

Many prey species induce defences in direct response to predation cues. However, prey defences could also be enhanced by predators indirectly via mechanisms that increase resource availability to prey, e.g. trophic cascades. We evaluated the relative impacts of these direct and indirect effects on the mechanical strength of the New Zealand sea urchin Evechinus chloroticus. We measured crush-resistance of sea urchin tests (skeletons) in (i) two marine reserves, where predators of sea urchins are relatively common and have initiated a trophic cascade resulting in abundant food for surviving urchins in the form of kelp, and (ii) two adjacent fished areas where predators and kelps are rare. Sea urchins inhabiting protected rocky reefs with abundant predators and food had more crush-resistant tests than individuals on nearby fished reefs where predators and food were relatively rare. A six-month long mesocosm experiment showed that while both food supply and predator cues increased crush-resistance, the positive effect of food supply on crush-resistance was greater. Our results demonstrate a novel mechanism whereby a putative morphological defence in a prey species is indirectly strengthened by predators via cascading predator effects on resource availability. This potentially represents an important mechanism that promotes prey persistence in the presence of predators.

Predation cues rather than resource availability promote cryptic behaviour in a habitat-forming sea urchin

It is well known that predators often influence the foraging behaviour of prey through the so-called “fear effect”. However, it is also possible that predators could change prey behaviour indirectly by altering the prey’s food supply through a trophic cascade. The predator–sea urchin–kelp trophic cascade is widely assumed to be driven by the removal of sea urchins by predators, but changes in sea urchin behaviour in response to predators or increased food availability could also play an important role. We tested whether increased crevice occupancy by herbivorous sea urchins in the presence of abundant predatory fishes and lobsters is a response to the increased risk of predation, or an indirect response to higher kelp abundances. Inside two New Zealand marine reserves with abundant predators and kelp, individuals of the sea urchin Evechinus chloroticus were rarer and remained cryptic (i.e. found in crevices) to larger sizes than on adjacent fished coasts where predators and kelp are rare. In a mesocosm experiment, cryptic behaviour was induced by simulated predation (the addition of crushed conspecifics), but the addition of food in the form of drift kelp did not induce cryptic behaviour. These findings demonstrate that the ‘fear’ of predators is more important than food availability in promoting sea urchin cryptic behaviour and suggest that both density- and behaviourally mediated interactions are important in the predator–sea urchin–kelp trophic cascade.