繁茂膜海绵滤食养殖水体中过剩饵料的研究

繁茂膜海绵(Hymeniacidon perleve)可滤食养殖水体中的残饵。对活体饵料新月菱形藻(Natzchia closterum),在无营养盐条件,5 g鲜重海绵处理300 mL,藻数量为1.62×106/mL的藻液240 h后,处理组藻的平均浓度仅为对照组的2.9%,为初始浓度的17.2%;在有营养盐条件,5g鲜重海绵处理300 mL,藻数量为0.87×106mL-1的藻液220 h后,对照组的藻仍处于指数生长期,此时处理组藻的平均浓度仅为对照组的0.05%,为初始浓度的64.4%。对死体海参饵料—藻粉和鱼粉蛋白等,由于海绵的滤食作用,海水中颗粒物的浓度随时间增加而呈指数曲线降低。1.5 g鲜重海绵处理200 mL,含200 mg/L海参饵料的海水,在第4d时,海绵已滤食72.6%的颗粒物,有机颗粒物的最大比截留速率为21.6×10-3/d.L。同时,海绵的生物量明显增加。     

Pre-and Post-Liming Aquatic Communities and Trout Diets

In the period following liming and before the introduction of brown trout to Loch Fleet, there was a reduction in the numbers of invertebrates, including the Chironomidae, Oligochaeta and Hydracarina in the loch, but an overall increase in invertebrates in the inlet and outlet streams. This was followed in the loch by a recovery in the numbers of certain groups (particularly the Trichoptera and Ephemeroptera) to pre-liming levels in spite of the introduction of the trout.

The diets of the trout comprised a wide variety of aquatic and terrestrial organisms ranging in size from Fprotozoans to newts and are dominated by chironomids. Opportunistic type of feeding as found in the present study appears to be typical of the brown trout and is reported for many water bodies by other workers.

Significant differences (P < 0.05 and P < 0.001) were found in the numbers and weights of certain food organisms in the stomachs of brown trout caught by different fishing methods in the summers of 1992 and 1993. Fish caught by gill net contained fewer planktonic crustaceans and chironomids, but greater numbers of trichopterans and terrestrial organisms, than in those caught by fly and spinner. the differences are probably related to differences in the depth at which the fish, caught by the various methods, were feeding.     

On vegetarianism,morality, and science: A counter reply

I recently took issue with Kathryn George's contention that vegetarianism cannot be a moral obligation for most human beings, even assuming that Tom Regan's stringent thesis about the equal inherent value of humans and many sentient nonhumans is correct. I argued that both Regan and George are incorrect in claiming that his view would permit moral agents to kill and eat innocent, non-threatening rights holders. An unequal rights view, by contrast, would permit such actions if a moral agent's health or life is at stake. I then argued that current nutritional research does not support Professor George's claim that some wealthy adult males (and many fewer wealthy women) are the only persons whose health does not require the consumption of nonhuman animals and their products. In her 1992 response to my critique, George did not address my moral argumentation. She concentrated her entire paper on a wholesale rejection of my discussion of nutrition. Although she now takes a somewhat more moderate position on who can safely contemplate strict vegetarianism, she still believes that most people are not in a position to follow such a diet. In my counter-reply, I argue that her rejection is based upon numerous distortions, omissions, and false charges of fallacy. She even devotes a substantial section of her paper to criticizing me for saying the opposite of what I actually wrote. As I did in my earlier paper, I cite current research, including George's own preferred source on the topic of vegetarianism, to support my view. I conclude that Professor George has still not shown that for most human beings it is dangerous to follow a diet that omits nonhuman animals and their products. Moral agents who take the rights of humansand nonhumans seriously will find vegetarianism well worth considering.     

Nutritional risks of vegan diets to women and children: Are they preventable?

The potential health risks of vegan diets specifically for women and children are discussed. Women and children are at higher risk of malnutrition from consumption of unsupplemented vegan diets than are adult males. Those who are very young, pregnant, lactating, elderly, or who suffer from poverty, disease or other environmentally induced disadvantages are at special risk. The size of these risks is difficult to quantify from existing studies. Fortunately the risk of dietary deficiency disease can be avoided and the potential health benefits of vegan diets can be realized when diets for these groups are planned in line with theRecommended Dietary Allowances so that nutrient intakes reach or exceed recommended levels, and access to preventive and curative health services is assured.     

Evaluating the sustainability of diets–combining environmental and nutritional aspects

This study examined two methods for jointly considering the environmental impact and nutritional quality of diets, which is necessary when designing policy instruments promoting sustainable food systems. Both methods included energy content and 18 macro- and micronutrients in the diet, the climate impact, land use and biodiversity damage potential. In Method 1, the content of different nutrients in the diet was normalised based on recommended intake or upper levels for average daily intake and presented together with the environmental impacts, which were normalised according to estimated sustainable levels. In Method 2, the nutritional quality of different diets was considered by calculating their nutrient density score, and the environmental impact was then expressed per nutrient density score. Three diets were assessed; a diet corresponding to Nordic recommendations, the current average Swedish diet and a lifestyle Low Carbohydrate-High Fat (LCHF) diet. Method 1 clearly showed that the climate impact was far beyond the sustainable level for all diets, while land use was within the sustainability limit for the recommended diet, but not the other two. Comparisons based on nutrient density scores depended on the score used, but the current and LCHF diets had more impact than the recommended diet (less livestock products) for all but one score. Over- and under-consumption of nutrients were clearly shown by Method 1 but not possible to distinguish with Method 2, as normalisation was not possible, making it difficult to evaluate the absolute scale of the impacts when nutrient density scores were used. For quantitative information on the environmental and nutritional impacts of diets as support in decision-making processes, it is important that data presentation is transparent. There is limited value in reducing results to a low number of indicators that are easy to read, but difficult to interpret, e.g. nutrient density score. Method 1 allows combined assessment of diets regarding environmental impact and nutritional intake and could be useful in dietary planning and in development of dietary recommendations and other policy instruments to achieve more sustainable food systems.     

Interspecific interactions of amphipods <Emphasis Type="Italic">Gammarus lacustris</Emphasis> and <Emphasis Type="Italic">Gmelinoides fasciatus</Emphasis>

Experimental studies of interactions between two amphipod species (Gmelinoides fasciatus and Gammarus lacustris) showed that predation is the basic mechanism accounting for their mutual exclusion in nature. Mortality from predation among similar-sized specimens of both species at an equal abundance ratio was similar (24–25% in G. lacustris and 27–30% in G. fasciatus). The displacement of G. lacustris by G. fasciatus was observed when the latter was dominant. Adult G. fasciatus and G. lacustris successfully preyed on juveniles of their competitors and did not differ significantly in daily food consumption as a percentage of body weight: 6–24% at a fresh body weight of 18–24 mg in both species. The potential for rapid population growth under new conditions contributed to the success of the invasive Baikal species G. fasciatus in displacing G. lacustris from many water bodies of Russia.