Marine macroalgae as food for earthworms: growth and selection experiments across ecotypes

Abstract

Historically, subsistence farmers around the Atlantic coast of NW Europe utilized marine algae as a fertilizer in agroecosystems, a practice that continued in small areas and is now considered to have real potential for re-establishing sustainable food production systems on marginal soils. Earthworms form a significant component of soil fauna, and their ecosystem services are welldocumented. Therefore, palatability of marine organic amendments to faunal detritivores of terrestrial systems is of interest. This work aimed to assess the potential for growth of Aporrectodea caliginosa, Lumbricus rubellus and Aporrectodea longa fed with two common macroalgae (seaweeds), Laminaria digitata and Fucus serratus. In addition, choice chambers were constructed to permit earthworm selection of these macroalgae with more conventional organic materials, horse manure (HM) and birch leaves (BL). Over a period of 2 months, earthworm species showed significantly greater mass gain with conventional food (p < 0.05). Laminaria outperformed Fucus, which in turn was superior to soil alone. Similarly, when given a choice, a significant preference (p < 0.001) was shown for the more nitrogen-rich HM and BL over the seaweeds. No removal was recorded for A. caliginosa when offered seaweeds only. By contrast, L. rubellus and A. longa showed significant preferences (p < 0.001) for Laminaria over Fucus and fresh material over degraded. These results underline an interest to profit from natural resources (seaweeds) to maintain or improve soil biological quality in marginal coastal areas. Keywords Agroecosystems. Birch leaves. Choice chamber. Earthworm. Fucus serratus. Horse manure. Laminaria digitata. Macroalgae. Seaweed Highlights •Earthworms will consume macroalgae and show mass gain, especially with Laminaria •Given a choice, macroalgae are not preferred to more conventional food materials •Treatment of macroalgae in a variety of ways may enhance consumption •Selected earthworm species show different behaviours when provided with a choice of macroalgae and other organic material

Seaweed extract effect on arbuscular mycorrhizae spore in soil engineered by earthworm, and the soil effect on upland rice growth

“…Meanwhile, the tendency of cocoons and immature occurred in the concentration of 60% (C60) (Table 1). These results re-emphasized that the application of K. alvarezii extract through the soil did not have a significant effect on reducing microbe populations [28], especially from the Phertima sp. 1±2a 1±2a 17±4a 20±4a Note: Numbers followed by the same letter in the same column showed no significant difference according to the LSD test at the p < 0.05 level.…”

“…The survival of Pheretima sp was caused by the application of seaweed extracts to the soil, which further triggered their activities in modulating bacteria and fungi that were positively correlated with plant productivity [28]. Based on the soil fungi group, AMF played a functional role in facilitating plant access to nutrients and water, as well as stimulating root growth [29].…”

Earthworms in past and present agricultural landscapes of Hebridean Scotland

“…In low input agricultural systems where fertilisation is organic, earthworms can notably increase plant yield through enhancement of nitrogen cycling and availability [40] and possibly by similar effects on soil phosphorus [41]. It has been recently shown that earthworms can feed on kelp [9], the main organic amendment used at our study sites, and potentially increase the mineralisation of plant nutrients from it. In the lazybeds, both abandoned and presently active, earthworms were present in sufficiently high numbers for effects on nutrient cycling and plant growth to be anticipated.…”

“…Combined with high annual rainfall up to, for instance, 1,800 mm on the Isle of Rum [7], these soils require management to make them viable for crop production. Many coastal soils were amended with brown seaweeds (kelp and fucoids) [8] produced in abundance in the littoral zone and collected from the shore, often after storm dislodgement [9]. In some areas this marine bounty was simply applied directly to the land or may have been composted first, perhaps with the addition of animal dung [10].…”

“…The aims of this investigation were to gather specific data on the earthworms present at selected current and/or previous agricultural sites in the Hebrides where seaweed was, or is still, used as a fertiliser. The Isle of Rum with historical lazybed formations (Figure 2a) was chosen to complement ongoing soil ecological research on the island [9,14,[18][19][20]. Two further, contrasting locations were selected: organic, anthropic, agricultural soils (Blacklands) of North Uist and sandy, fertile, low-lying grassy pasture (Machair) of South Uist (Figures 2b and 2c respectively).…”