Islay D. Marsden

Kelp-sandhopper interactions on a sand beach in New Zealand. I. Drift composition and distribution

Abstract The composition of organic matter deposited on a New Zealand sand beach was measured monthly during neap tide periods over an annual cycle. The main components of the drift were wood, grass and two kelp species, Macrocystis pyrifera (L.) C.Ag. and Durvillaea antarctica (Chamisso) Hariot. Drift composition was measured from five transects, 5 m in width extending from the base of the dunes (EHWS) to the low tide level. The average wet weight of material collected from the 5-m beacg strip was 11.23 kg (SE 3.78), with low values in summer (December and January) and highest biomass in July. Variability in organic matter was due to fluctuating levels of M. pyrifera , which dominated the summer periods, ranging from 0.07 to 2.2 kg·m −1 strip of beach. The biomass of D. antarctica decreased downshore, contrasting with M. pyrifera which was generally distributed evenly down to 20 m from the base of the dunes. The amphipod Talorchestia quoyana (Milne-Edwards) was closely asociated with drift material, especially fresh M. pyrifera . Distribution patterns and density of T. quoyana varied with season, shore level and substratum type. Exceptional densities of T. quoyana ( x= 121750m −2 ) were found associated with M. pyrifera on the drift line. There were two peaks of juvenile recruitment during which juveniles were also associated with sand away from drift material. Results from core samples suggest no direct relationship between sandhopper density and algal biomass on a seasonal basis. Annual deposition of kelp onto the sand beach was estimated as −1 , characterized by regular input due to storm and seasonal events. The spatial distribution of T. quoyana was dependent on the availability of drift wrack and this is discussed in relation to its behavioural and physiological tolerances of the environmental factors operating on the sand beach.

Seasonal variation in the reproductive activity and biochemical composition of the Pacific oyster (Crassostrea gigas) from the Marlborough Sounds, New Zealand

Abstract Reproductive cycles of the Pacific oyster Crassostrea gigas (Thunberg) from the Marlborough Sounds, New Zealand, were followed between June 1998 and January 2000. Histological examination of the gonad confirms an annual cycle with a winter inactive period followed by rapid gonad development and a single short spawning period. The population gonad index correlated with seawater temperature and changes in tissue dry weight, condition index, and biochemical components. In winter, few individuals with early gametogenic stages were present and rapid development of primary oocytes (diam. 11 μm) occurred during spring (September‐November). The developmental rate and the diameter of mature oocytes (37 μm) was similar for the 1998 and 1999 seasons. For a standard 110‐mm‐length oyster, maximal tissue body weight and condition index were recorded in December. Rapid weight loss in January was length dependent and was attributed to spawning. Temperature was the environmental variable which best correlated with the timing of gametogenesis. Food availability (phytoplankton biomass) may have been responsible for inter‐annual variations. The biochemical composition (% glycogen, lipid, protein) of separated gonad and somatic tissues were variable seasonally and annually. Gametogenesis (oocyte diameter) was associated with increased gonad protein and glycogen and a decrease in lipid concentrations. These changes are similar to those in Pacific oyster populations from other parts of the world.

Kelp-sandhopper interactions on a sand beach in New Zealand. II. Population dynamics of Talorchestia quoyana (Milne-Edwards)

Abstract The population structure and breeding biology of the supralittoral sandhopper Talorchestia quoyana (Milne-Edwards) were investigated over an annual cycle in relation to the availability of drift kelp Macrocystis pyrifera (L.) C.Ag. At neap tides the population was dispersed with amphipods associated with freshly deposited wrack and gravid females separated from other individuals. Size distributions were dominated by immature individuals. Recruitment occured throughout the year except during winter. Growth rates depended on sex and body size with a juvenile growth rate of 1.7 mm length·month −1 . Average life span was ≈ 13months . There was no direct relationship between brood size and female length, the average brood size for a female length 16.2 mm was 20.5. Brood mortality during embryological development was low, egg volume was high, rapidly increasing during the later stages resulting in the release of large hatchlings. Amphipod biomass varied with shore level, habitat type and season. Biomass estimates were less variable than density and both showed little correlation with kelp biomass. Estimates of dry weight amphipod biomass · 5 m −1 strip of beach ranged from 5.8 g (winter) to 1.2 kg (spring). The ratio of amphipod biomass to kelp standing stock varied with shore level and season due to irregular input of M. pyrifera . The population characteristics and breeding biology, of this sandhopper allow exploitation of san-beach habitat which receives regular but low levels of kelp input.

Bimodal respiration, water balance and acid-base regulation in a high-shore crab, Cyclograpsus lavauxi H. Milne Edwards

Cyclograpsus lavauxi H. Milne Edwards, 1853 occurs under boulders near the littoral fringe, where it is wetted only briefly, if at all, in each tide. Mean water content of sea-water equilibrated crabs was 62.3 % of body weight. On warm, windy days crabs on the shore lose > 17.5% of body water. Water loss for crabs of 1.6 g mean body weight was 0.29 % water content · h −1 · mm Hg saturation deficit −1, which is similar to that of species occupying positions lower on the shore. C. lavauxi is, however, able to tolerate comparatively greater losses of body water (up to 36%) compared with species from lower shore levels. As the gills dry, the lamellae separate into regular clumps which may help to maintain gas exchange. Resting oxygen consumption (Vo2) after 3–5 h settlement was similar in water and air. During enforced activity, Vo2 increased by factors of 5.3 in water and 2.6 in air at a standardized body weight of 1.5 g, indicating an appreciable aerobic scope in both media. Loss of up to 16% of body water did not depress resting aerial Vo2 or aerobic scope. In resting crabs there was no change in haemolymph pH after 24 h of either immersion or emersion, but haemolymph [Ca2+], [HCO−3] + [CO2−3], and calculated Pco2 all rose in air relative to aquatic values. These results suggest that cuticular or other endogenous CaCO3 is mobilized to compensate the respiratory acidosis in air. The implications of such physiological properties for aquatic and aerial activity on the shore are discussed.

The influence of salinity on copper accumulation and its toxic effects in estuarine animals with differing osmoregulatory strategies

Copper is an important ionoregulatory toxicant in freshwater, but its effects in marine and brackish water systems are less well characterised. The effect of salinity on short-term copper accumulation and sublethal toxicity in two estuarine animals was investigated. The osmoregulating crab Hemigrapsus crenulatus accumulated copper in a concentration-dependent, but salinity-independent manner. Branchial copper accumulation correlated positively with branchial sodium accumulation. Sublethal effects of copper were most prevalent in 125% seawater, with a significant increase in haemolymph chloride noted after 96h at exposure levels of 510 microg Cu(II) L(-1). The osmoconforming gastropod, Scutus breviculus, was highly sensitive to copper exposure, a characteristic recognised previously in related species. Toxicity, as determined by a behavioural index, was present at all salinities and was positively correlated with branchial copper accumulation. At 100% seawater, increased branchial sodium accumulation, decreased haemolymph chloride and decreased haemolymph osmolarity were observed after 48h exposure to 221 microg Cu(II) L(-1), suggesting a mechanism of toxicity related to ionoregulation. However, these effects were likely secondary to a general effect on gill barrier function, and possibly mediated by mucus secretion. Significant impacts of copper on haemocyanin were also noted in both animals, highlighting a potentially novel mechanism of copper toxicity to animals utilising this respiratory pigment. Overall these findings indicate that physiology, as opposed to water chemistry, exerts the greatest influence over copper toxicity. An understanding of the physiological limits of marine and estuarine organisms may be critical for calibration of predictive models of metal toxicity in waters of high and fluctuating salinities.

Assessment of a mussel as a metal bioindicator of coastal contamination: relationships between metal bioaccumulation and multiple biomarker responses.

This is the first study to use a multiple biomarker approach on the green-lipped mussel, Perna canaliculus to test its feasibility as a bioindicator of coastal metal contamination in New Zealand (NZ). Mussels were collected from six low intertidal sites varying in terms of anthropogenic impacts, within two regions (West Coast and Nelson) of the South Island of NZ. Trace elements, including arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), nickel (Ni), and zinc (Zn), were measured in the gills, digestive gland, foot and mantle, and in the surface sediments from where mussels were collected. Metal levels in the sediment were relatively low and there was only one site (Mapua, Nelson) where a metal (Ni) exceeded the Australian and New Zealand Interim Sediment Quality Guideline values. Metal levels in the digestive gland were generally higher than those from the other tissues. A variety of biomarkers were assessed to ascertain mussel health. Clearance rate, a physiological endpoint, correlated with metal level in the tissues, and along with scope for growth, was reduced in the most contaminated site. Metallothionein-like protein content and catalase activity in the digestive gland, and catalase activity and lipid peroxidation in the gill, were also correlated to metal accumulation. Although there were few regional differences, the sampling sites were clearly distinguishable based on the metal contamination profiles and biomarker responses. P. canaliculus appears to be a useful bioindicator species for coastal habitats subject to metal contamination. In this study tissue and whole organism responses provided insight into the biological stress responses of mussels to metal contaminants, indicating that such measurements could be a useful addition to biomonitoring programmes in NZ.

Biochemical biomarker responses of green-lipped mussel, Perna canaliculus, to acute and subchronic waterborne cadmium toxicity

The biochemical responses of the green-lipped mussel, Perna canaliculus, to waterborne cadmium (Cd) were investigated in order to delineate toxic mechanisms, and the impacts of exposure dose and duration, of this important toxicant in a potential sentinel species. Mussels were exposed for either 96 h (acute: 0, 2000, 4000 μgL(-1) Cd) or for 28 d (subchronic: 0, 200, 2000 μgL(-1) Cd), and the digestive gland, gill and haemolymph were examined for impacts. Biochemical responses measured included those associated with metal detoxification (metallothionein-like protein; MTLP), oxidative stress (catalase, lipid peroxidation), cellular homeostasis (alkaline phosphatase, Na(+), K(+)-ATPase; NKA), and energy utilisation (glycogen, haemolymph protein). Following acute exposure, digestive gland glycogen and gill NKA activity were significantly altered by Cd exposure relative to levels in mussels exposed to Cd-free seawater. Subchronic Cd exposure resulted in a significant increase in MTLP levels in both the gill and the digestive gland. This increase was correlated strongly with the levels of Cd accumulation measured in these tissues (R=0.957 for gill, 0.964 for digestive gland). Catalase activity followed a similar pattern, although the correlation with tissue Cd accumulation was not as strong (R=0.907 for gill, 0.708 for digestive gland) as that for MTLP. Lipid peroxidation increased in the digestive gland at Days 7 and 14 at both subchronic Cd levels tested, but this effect had largely dissipated by Days 21 and 28 (with the exception of the 2,000 μgL(-1) group at Day 28). Alkaline phosphatase activity decreased significantly with Cd exposure in both tissues. This effect was observed at both tested concentrations in the gill, but only at the highest concentration for digestive gland. A decrease in digestive gland glycogen levels was observed in Cd-exposed mussels (Days 14 and 21 at 2,000 μgL(-1)), while haemolymph protein levels increased as a result of subchronic Cd exposure. These findings indicated that biochemical responses in Cd-exposed mussels were tissue-specific, dose- and time-dependent, with duration of exposure being the predominant effect. This study shows that biochemical changes in Cd-exposed green-lipped mussels can be linked to tissue metal accumulation and are consistent with previously reported physiological effects. It also suggests that green-lipped mussels are amenable to a multiple biomarker approach and may be of use as a bioindicator species for monitoring coastal metal pollution.

Impairment of green-lipped mussel (Perna canaliculus) physiology by waterborne cadmium: Relationship to tissue bioaccumulation and effect of exposure duration

Laboratory studies were performed to assess the impact of acute and subchronic cadmium (Cd) exposure on the green-lipped mussel, Perna canaliculus. A 96 h median lethal concentration (LC(50)) value of 8160 μg L(-1) was determined, characterising this species as relatively tolerant to Cd exposure. Acute (96 h; at 2000 and 4000 μg Cd L(-1)) and subchronic (28 d; at 200 and 2000 μg Cd L(-1)) waterborne exposures were then conducted to investigate the impact of Cd exposure on physiological responses (e.g. clearance (feeding) rate, absorption efficiency, oxygen uptake, ammonia production, oxygen to nitrogen ratio, scope for growth) and tissue Cd accumulation. Cd accumulation in digestive gland showed saturation with respect to increasing exposure concentration, while the gill tissue Cd accumulation followed a positive linear relationship with Cd exposure level. Clearance rates declined during both acute and subchronic exposures at levels of 2000 μg Cd L(-1) or higher. Impairments of clearance rates were strongly correlated with tissue Cd accumulation. Coupled with their importance as a food source, and their wide coastal distribution, these data suggests that P. canaliculus may be a species useful as an indicator species for trace metal pollution in coastal environments.

Effects of aerial exposure on oxygen consumption by the New Zealand mussel Perna canaliculus (Gmelin, 1791) from an intertidal habitat

Abstract Aquatic and aerial oxygen uptake were measured for Perna canaliculus (Gmelin) (length 20–60 mm) collected from mid-tide and low tide levels of a rocky shore during summer and winter. Oxygen uptake increased with tissue dry weight in aquatic and to a lesser extent aerial conditions at most temperatures investigated, 10, 15 and 20°C in summer and 5, 10 and 15°C in winter. Aerial exposure reduced oxygen uptake up to 87% of the aquatic value with greater reduction at higher exposure temperatures. Oxygen uptake was similar in mussels from both shore levels and there was no pronounced increase in the aquatic oxygen consumption of mid-shore individuals. There was little evidence of seasonal adjustment in the aquatic oxygen uptake rate–temperature ( R – T ) curve for mussels from either mid- or low-shore levels; generally oxygen uptake increased at higher exposure temperatures. In contrast, oxygen uptake of P. canaliculus in air was generally reduced at higher exposure temperatures, and there was a small seasonal acclimatory response. Calculations of the daily oxygen requirements of mussels from the two shore levels suggest energy savings of 35% for mid-shore mussels during summer due to reduced oxygen demand in aerial conditions at higher temperatures.

Aerial and aquatic respiration in two mud crabs, Helice crassa dana (Grapsidae) and Macrophthalmus hirtipes (Jacquinot) (Ocypodidae), in relation to habitat

Abstract 1. 1. Weight-specific oxygen uptake by Macrophthalmus hirtipes and Helice crassa was a decreasing function of dry tissue body-weight and generally increased at higher temperatures. 2. 2. Oxygen consumption by small crabs, of each species, was less temperature dependent than for larger individuals. 3. 3. Both species displayed short-term metabolic compensation at temperatures commonly encountered in the field. Such compensation was especially pronounced (Q10 values 4. 4. At the temperature of acclimation, in both air and seawater, H. crassa consumed more oxygen than M. hirtipes. Also, relative to M. hirtipes, H. crassa was better able to utilize atmospheric oxygen. 5. 5. Results are discussed in relation to the habitat preferences and characteristic vertical separation of each species.