Nutrient ratios in bass tissue tracked the abundance of a fish parasite

In 11 experimental ponds, nitrogen-to-phosphorus ratios in bass digestive tissue reflected water nutrients and parasite levels.

Editorial illustration — not from the study.

Researchers manipulated nutrient availability in 11 ponds stocked with piscivorous largemouth bass and measured nutrients, fish and invertebrate consumers, and Crepidistomum parasites in the bass’s pyloric caeca, a digestive organ. Fertilization increased phosphorus in the water and fine particulate organic matter while lowering their carbon-to-phosphorus and nitrogen-to-phosphorus ratios.

The nitrogen-to-phosphorus ratio in bass pyloric caeca was inversely related to both total phosphorus in the water and the abundance of Crepidistomum in the tissue. The researchers did not detect fertilization effects on intermediate trophic levels, which include potential hosts for the parasite.

What the bass tissue showed

Fertilization increased total phosphorus and reduced carbon-to-phosphorus and nitrogen-to-phosphorus ratios in pond water and fine particulate organic matter. The researchers found no detected fertilization effects on intermediate trophic levels. In bass pyloric caeca, nitrogen-to-phosphorus ratios were inversely related to total phosphorus in the water column and to Crepidistomum abundance. These tissue nutrient ratios explained more variation in parasite abundance than any other measured variable.

Why the nutrient link matters

The findings suggest that nutrient ratios in a predator’s digestive tissue can provide an informative link between nutrient availability at the base of a pond ecosystem and the abundance of a parasite that moves through the food web. This could give researchers a tissue-based measure for studying how ecosystem nutrients relate to parasites, although the study does not establish that the tissue ratios caused changes in parasite abundance.

Evidence and open questions

This was a controlled experiment in 11 ponds stocked with largemouth bass over three months. The study found relationships between water nutrients, bass tissue nutrient ratios and parasite abundance, but it could not determine whether the tissue ratios directly influenced Crepidistomum or instead reflected other ecosystem changes that affected the parasite. The abstract also reports no detected effects of fertilization on intermediate trophic levels, and the findings come from this experimental pond setting and time period.

New maps show where rocks from Stromboli explosions could land

Researchers have produced probability maps showing where rocks thrown out by major explosions and paroxysms at Stromboli could fall. The maps identify exposed areas and estimate the chance of fallout over the next 10 and 50 years.

22 hours ago·7 views

Climate & Environment

Discarded drug capsules become water-cleaning carbon and mineral ash

Researchers converted discarded gelatin capsules into porous activated carbon and mineral-rich ash. The carbon adsorbed methylene blue, acetaminophen and bisphenol A, while one ash material removed about 70% of methylene blue under ultraviolet light after 350 minutes.

1 day ago·8 views

Climate & Environment

Bumblebees spread tire-wear particles through colonies more than plastic ones

A study of buff-tailed bumblebees found that tire-wear particles were ingested by workers, transferred to larvae and added to nest materials more often than polystyrene particles. The findings suggest that studies of microplastic risks to pollinators should include particles from vehicle tires, not only standard laboratory plastics.