University of Maine at Machias

Abstract Climate change is one of the biggest challenges facing development and continuation of sustainable aquaculture in temperate regions. We primarily consider the ecological and physical resilience of aquaculture in the Gulf of Maine (GoM), where a thriving industry includes marine algae, extensive and intensive shellfish aquaculture, and a well‐established Atlantic salmon industry, as well as the infrastructure required to support these economically important ventures. The historical record of sea surface temperature in the GoM, estimated from gridded, interpolated in situ measurements, shows considerable interannual and decade‐scale variability superimposed on an overall warming trend. Climate model projections of sea surface temperature indicate that the surface waters in the GoM could warm 0.5–3.5°C beyond recent values by the year 2100. This suggests that, while variability will continue, anomalous warmth of marine heatwaves that have been observed in the past decade could become the norm in the GoM ca. 2050, but with the most significant impacts to existing aquaculture along the southernmost region of the coast. We consider adaptations leading to aquacultural resilience despite the effects of warming, larger numbers of harmful nonindigenous species (including pathogens and parasites), acidification, sea‐level rise, and more frequent storms and storm surges. Some new species will be needed, but immediate attention to adapt existing species (e.g. preserve/define wild biodiversity, breed for temperature tolerance and incorporate greater husbandry) and aquaculture infrastructure can be successful. We predict that these measures and continued collaboration between industry, stakeholders, government and researchers will lead to sustaining a vibrant working waterfront in the GoM.

We show that the application of linear vertex reinforcement to one dimensional nearest neighbor Markov processes, yielding associated vertex reinforced jump processes, preserves both recurrence and transience. The analog for discrete time linear bond reinforcement is due to Takeshima. This together with another result we prove adds to the numerous known parallels between these two reinforcements. Martingales are the primary tool used to study vertex reinforced jump processes.

Horseshoe crabs are valued for economic, ecological, and educational purposes. These values have raised interest in managing natural stocks and culturing crabs for conservation, research, and education. To inform these efforts, we used N and C stable isotopes to define the natural diet of juvenile horseshoe crabs and then assessed effects of different diets on growth and survival of juveniles in culture. In the natural environment, N and C isotope ratios in juvenile horseshoe crabs changed as crabs grew, with larger crabs consuming larger prey. Linear mixing analyses suggested young crabs were supported by high quantities of benthic and suspended particulate organic matter (POM), shifting between marine algae and salt marsh-based food webs, depending on size. In culture, we tested the relative importance of algae, as a proxy for POM, in horseshoe crab diet by feeding juvenile crabs different percentages of algae and prey animals. Initially, juvenile crabs showed a significant increase in size when fed diets >70% protein, but showed a decrease in survival compared to algae-rich diets. Overall, growth rates and survival declined through time during the 128-day study, regardless of diet composition. These data suggest horseshoe crabs require foods from a combination of plant and animal sources. Successful culture or conservation of horseshoe crabs will depend on understanding the relative importance of different food sources at different life stages as well as discerning the balance between factors that increase growth, but reduce survival.

A series of intertidal field experiments was conducted from 1986–2003 in eastern Maine to examine biotic and abiotic factors influencing the growth and survival of wild and cultured individuals of the softshell clam, Mya arenaria L. Separate experiments examined: (1) the efficacy of transferring sublegal wild clams (<50.8 mm SL) from areas near the high intertidal zone where shell growth was slow to areas where growth was predicted to be faster; (2) effects of tidal height on wild and cultured clam growth; (3) effects of spatial variation on cultured clam growth; (4) dispersion and growth of cultured juveniles in small experimental units; (5) effects of the naticid gastropod, Euspira heros Say, predation on survival of wild and cultured clams and (6) the species composition of large, crustacean predators that forage intertidally during periods of tidal inundation. Protective netting (4.2 mm aperture) increased recovery rate of transferred clams by 120% and resulted in a 3-fold enhancement of wild recruits. Effects of tidal height on wild clam growth revealed complex behaviors in >0 y-class individuals. Clams growing near the upper intertidal take >8 y to attain a legal size of 50.8 mm SL, whereas animals near the mid intertidal generally take 4.5–6.5 y. Unexpectedly, clams initially 38–54 mm SL and growing near the extreme low tide mark at a mud flat in Eastport, Maine, added, on average, <2 mm of new shell in a year, which was 8–10 mm SL less than animals at higher shore levels. It is hypothesized that biological disturbance by moon snails, that consumed >90% of clams at the low shore levels, contributed to this slow growth. In another field trial from 1986–1987, moon snails and other consumers were allowed access to clams ranging in size from 15–51 mm. E. heros preyed on clams over the entire size range and attacked clams between 31–40 mm at a rate that was nearly double what had been expected. Mean snail size was estimated to range from 10–52 mm shell height (SH), based on a laboratory study that yielded information about the linear relationship between snail size and its borehole diameter. In an experiment from June to September 1993, moon snails consumed >70% of juvenile clams (ca. 10 mm SL) within a month after planting at each of three tidal heights. Snail sizes ranged from 15–20 mm SD with larger individuals occurring near the upper intertidal zone. Green crabs, Carcinus maenas (L.) also prey heavily on softshell clam populations, but most studies that use shell damage to assign a predator have assumed that all crushing and chipping predation is because of this invasive species. An intertidal trapping study demonstrated that both green crabs and rock crabs, Cancer irroratus Say, are present during periods of tidal inundation, with the latter species accounting for ca. 40% of large crustacean numbers.

Although the computer science literature contains numerous examples that describe various interactive evolutionary computational (IEC) algorithms, few studies have focused on how use such algorithms to elicit design information from a population of human users. The purpose of this study was to address this gap in the literature by constructing and testing an IEC algorithm for anthropomorphic symbol design. A design group of 25 subjects used the algorithm to create 100 anthropomorphic symbols represented the emotions of anger, joy, fear, and sadness. The 100 symbols underwent comprehensions testing using a separate group of 30 subjects. Factor analysis of the nine limb angles comprising each symbol revealed that specific combinations of limb angles differed significantly between symbols based on the emotional referent the IEC algorithm users meant to convey. Comprehension testing results revealed that recognition accuracy for the joy symbols was highest while recognition accuracy for the anger symbols was lowest. The findings of the current study suggest the IEC algorithms can be used to identify important symbol design characteristics and generate symbols whose message is readily comprehended by end user populations.

Humic substances are precursors of carcinogenic trihalomethanes (THMs) formed during disinfection by chlorination in water treatment processes. In an effort to understand the relationship between trihalomethane formation potential (THMFP) and physicochemical properties of humic substances, UV-visible absorbance, fluorescence in emission and synchronous scan modes, and NMR spectra were measured for several aquatic fulvic and humic acids. For comparison, a soil fulvic acid was also examined using these methods. The feasibility of the gradient modified spin-echo (GOSE) NMR experiment to selectively measure singlet resonances arising from isolated protons was examined. In addition, diffusion coefficients were measured for DMSO solutions of the fulvic acids using BPPLED and GOSE-edited pulse sequences. Although none of the methods tested produced results that correlated with THMFP, the GOSE intensities determined for different regions of the NMR spectra did reflect the relative abundance of different types of functional groups produced by lignin oxidation. In addition, the GOSE-edited diffusion results suggest that the isolated protons, those most reactive to chlorination, are more likely contained in the larger molecular weight fractions of fulvic acids.

The Byzantine and Early Islamic Near East: Problems in the Literary Source Material, edited by Averil Cameron &amp; Lawrence I. Conrad (Studies in Late Antiquity and Early Islam: 1) 428 pages, map, photo, index. Princeton, NJ: Darwin Press, 1992. $29.95 (Cloth) ISBN 0-87850-080-4 - Volume 28 Issue 1