Variation in a host-epiphyte relationship along a wave exposure gradient

The red alga Polysiphonia lanosa (L ) Tandy is an obligate epiphyte that primarily occurs on the fucoid brown algal basiphyte Ascophyllum nodosum (L) Le Jolis In the present study we examine how epiphytic interactions between P lanosa and A nodosum vary along a wave exposure gradient within the southern Gulf of Maine, USA P lanosa was most dense on protected shores, however because the stature of P lanosa was greater on exposed than on sheltered shores, greater biomass occurred In exposed habitats Epiphytlc P lanosa pnmanly attached to inlured vegetative bssue at exposed sites, while ~ t osc currence was primarily receptacular at sheltered sites A significantly stronger correlation was found between host receptacle abundance and epiphyte abundance at a protected low than an exposed site As a result, the distribution of epiphytes along the host S stlpe vanes at different sites We suggest that changes in the distribution and abundance of P lanosa across this wave exposure gradient are highly influenced by vanations in the distribution and persistence of suitable attachment sites on the host plant Because both the quantity and quality of attachment sites vanes w t h exposure, we hypothesize that d~fferenpt rocesses limit or de t e rm~neP lanosa populations in different locations In protected sites P lanosa may be limited by the presence of adequate substrata (inlured bssue and lateral pits) where successful recruitment may occur By contrast at exposed sites the supply of P lanosa sporelings, rather than quantity of appropnate substrata, may limlt population size

Tracking environmental trends in the Great Bay Estuarine System through comparisons of historical and present-day green and red algal community structure and nutrient content

Monitoring macroalgae populations is an effective means of detecting long term water quality changes in estuarine systems. To investigate the environmental status of New Hampshire’s Great Bay National Estuarine Research Reserve, this study assessed the abundance/distribution of macrophytes, particularly Gracilaria and Ulva species, relative to eutrophication patterns; compared historical (1970s-1990s) and current algal biomass/cover at several sites; and compared Ulva and Gracilaria tissue N/P content to ambient and historical levels. Ulva and Gracilaria biomass/cover have increased significantly at several sites. Cover by Ulva species, at seasonal maxima, was over 90 times the value recorded in the 1970s at Lubberland Creek, and exceeded 50% at all sites in the upper estuary. Gracilaria cover was greater than 25% at Depot Road in the upper estuary, whereas the historical measure was 1%. Sequencing of ITS2, rbcL and CO1 revealed the presence of previously undetected Ulva and Gracilaria species, including Gracilaria vermiculophylla (Ohmi) Papenfuss, an invasive species of Asian origin. Gracilaria vermiculophylla has exceeded G. tikvahiae as the dominant Gracilaria species in Great Bay. Historical voucher specimen screening suggests G. vermiculophylla was introduced as recently as 2003. Nitrogen and phosphorus levels are elevated in the estuary. We should expect continued seasonal nuisance algal blooms

Nonlinear characterisation of power ultrasonic devices used in bone surgery

Ultrasonic cutting has existed in surgery since the 1950s. However, it was not until the end of the 20th century that advances in ultrasonic tool design, transduction and control allowed commercially viable ultrasonic cutting devices to enter the market. Ultrasonic surgical devices, like those in other power ultrasonic applications such as drilling and welding, require devices to be driven at high power to ensure sufficient output motion is produced to fulfil the application it is designed to perform. With the advent of novel surgical techniques surgeons require tuned ultrasonic tools which can reduce invasiveness while giving access to increasingly difficult to reach surgical sites. To fulfil the requirements of novel surgical procedures new tuned tools need to be designed. Meanwhile, it is well documented that power ultrasonic devices, whilst driven at high power, are inherently nonlinear and, if no attempt is made to understand and subsequently control these behaviours, it is likely that these devices will suffer from poor performance or even failure. The behaviour of the commercial ultrasonic transducer used in bone surgery (Piezosurgery® Device) is dynamically characterised through finite element and experimental methods whilst operating in conjunction with a variety of tuned inserts. Finite element analysis was used to predict modal parameters as well as stress levels within the tuned devices whilst operating at elevated amplitudes of vibration, while experimental modal analysis validated predicted resonant frequencies and mode shapes between 0-80kHz. To investigate the behaviour of tuned devices at elevated vibrational amplitudes near resonance, responses were measured whilst the device was excited via the burst sine sweep method. In an attempt to provide an understanding of the effects that geometry, material selection and wavelength of tuned assemblies have on the behaviour of an ultrasonic device, tuned inserts consisting of a simple rod horn design were characterised alongside more complex cutting inserts which are used in maxillofacial and craniofacial surgery. From these results the aim will be to develop guidelines for design of tuned inserts. Meanwhile, Langevin transducers, commonly known as sandwich or stack transducers, in their most basic form generally consist of four parts; a front mass, a back mass, a piezoceramic stack and a stud or bolt holding the parts together under a compressive pre-load. It is traditionally proposed that the piezoceramic stack is positioned at or close to the vibrational nodal point of the longitudinal mode, however, this also corresponds with the position of highest dynamic stress. It is also well documented that piezoceramic materials possess a low linear stress threshold, therefore this research, in part, investigates whether locating the piezoceramic stack away from a position of intrinsic high stress will affect the behaviour of the device. Through experimental characterisation it has been observed that the tuned devices under investigation exhibited; resonant frequency shifts, jump amplitudes, hysteretic behaviour as well as autoparametric vibration. The source of these behaviours have been found to stem from device geometry, but also from heating within the piezoceramic elements as well as joints with different joining torques

Distribution, morphology, and genetic affinities of dwarf embedded Fucus populations from the Northwest Atlantic Ocean

Dwarf embedded Fucus populations in the Northwest Atlantic Ocean are restricted to the upper intertidal zone in sandy salt marsh environments; they lack holdfasts and are from attached parental populations of F. spiralis or F. spiralis x F. vesiculosus hybrids after breakage and entanglement with halophytic marsh grasses. Dwarf forms are dichotomously branched, flat, and have a mean overall length and width of 20.3 and 1.3 mm, respectively. Thus, they are longer than Irish (mean 9.3 mm) and Alaskan (mean 15.0 mm) populations identified as F cottonii. Reciprocal transplants of different Fucus taxa in a Maine salt marsh confirm that F spiralis can become transformed into dwarf embedded thalli within the high intertidal zone, while the latter can grow into F. s. ecad lutarius within the mid intertidal zone. Thus, vertical transplantation can modify fucoid morphology and result in varying ecads. Microsatellite markers indicate that attached F spiralis and F vesiculosus are genetically distinct, while dwarf forms may arise via hybridization between the two taxa. The ratio of intermediate to species-specific-genotypes decreased with larger thalli. Also, F s. ecad lutarius consists of a mixture of intermediate and pure genotypes, while dwarf thalli show a greater frequency of hybrids

INVESTIGATIONS OF NEW ENGLAND MARINE ALGAE VI: DISTRIBUTION OF MARINE ALGAE NEAR CAPE COD, MASSACHUSETTS

Volume: 76Start Page: 537End Page: 56

Macroalgal Monitoring in the Great Bay Estuary: 2018 Annual Report

Since 2013, the abundance and taxa of intertidal macroalgae have been assessed at fixed locations throughout the Great Bay Estuary in New Hampshire. Algal abundance may be influenced by environmental conditions such as nutrient levels, water temperature, light and invasive species. Therefore, abundance of different algal groups can provide insights into the overall health of the estuary and signal ecological change. In 2018, intertidal abundance data for percentage cover and biomass were collected, as planned, from five of the eight sites. For the first time, subtidal sampling arrays were also incorporated at all four sites in Great Bay proper to monitor macroalgae at lower elevations and to collect data on eelgrass communities coexisting with the algae