title: Abandonment and rapid infilling of a tide-dominated distributary channel at 0.7 ka in the Mekong River Delta

authors: Gugliotta, Marcello

abstract: The Ba Lai distributary channel of the Mekong River Delta was abandoned and infilled with sediment during the Late Holocene, providing a unique opportunity to investigate the sediment fill, timing and mechanisms of channel abandonment in tide-dominated deltaic systems. Based on analysis and age dating of four sediment cores, we show that the channel was active since 2.6 ka and was abandoned at 0.7 ka as marked by the abrupt disappearance of the sand fraction and increase in organic matter and sediment accumulation rate. We estimate that the channel might have been filled in a time range of 45–263 years after detachment from the deltaic network, with sediment accumulation rates of centimetres to decimetres per year, rapidly storing approximately 600 Mt of organic-rich mud. We suggest that the channel was abandoned due to a sediment buildup favoured by an increase in regional sediment supply to the delta. This study highlights that mechanisms for abandonment and infilling of tide-dominated deltaic channels do not entirely fit widely used models developed for fluvial-dominated environments. Their abandonment might be driven by autogenic factors related to the river-tidal and deltaic dynamics and favoured by allogenic factors (e.g., human impact and/or climate change).</jats:p>

text: Abandonment and rapid infilling of a tide-dominated distributary channel at 0.7 ka in the Mekong River Delta The Ba Lai distributary channel of the Mekong River Delta was abandoned and infilled with sediment during the Late Holocene, providing a unique opportunity to investigate the sediment fill, timing and mechanisms of channel abandonment in tide-dominated deltaic systems. Based on analysis and age dating of four sediment cores, we show that the channel was active since 2.6 ka and was abandoned at 0.7 ka as marked by the abrupt disappearance of the sand fraction and increase in organic matter and sediment accumulation rate. We estimate that the channel might have been filled in a time range of 45–263 years after detachment from the deltaic network, with sediment accumulation rates of centimetres to decimetres per year, rapidly storing approximately 600 Mt of organic-rich mud. We suggest that the channel was abandoned due to a sediment buildup favoured by an increase in regional sediment supply to the delta. This study highlights that mechanisms for abandonment and infilling of tide-dominated deltaic channels do not entirely fit widely used models developed for fluvial-dominated environments. Their abandonment might be driven by autogenic factors related to the river-tidal and deltaic dynamics and favoured by allogenic factors (e.g., human impact and/or climate change).</jats:p>

year: 2021

title: Physiological, kinematic, and electromyographic responses to kinesiology-type patella tape in elite cyclists

authors: Hébert-Losier, Kim

subjects: Science & Technology

abstract: Kinesiology-type tape (KTT) has become popular in sports for injury prevention, rehabilitation, and performance enhancement. Many cyclists use patella KTT; however, its benefits remain unclear, especially in uninjured elite cyclists. We used an integrated approach to investigate acute physiological, kinematic, and electromyographic responses to patella KTT in twelve national-level male cyclists. Cyclists completed four, 4-minute submaximal efforts on an ergometer at 100 and 200 W with and without patella KTT. Economy, energy cost, oxygen cost, heart rate, efficiency, 3D kinematics, and lower-body electromyography signals were collected over the last minute of each effort. Comfort levels and perceived change in knee stability and performance with KTT were recorded.

The effects of KTT were either unclear, non-significant, or clearly trivial on all collected physiological and kinematic measures. KTT significantly, clearly, and meaningfully enhanced vastus medialis peak, mean, and integrated electromyographic signals, and vastus medialis-to-lateralis activation. Electromyographic measures from biceps femoris and biceps-to-rectus femoris activation ratio decreased in either a significant or clinically meaningful manner. Despite most cyclists perceiving KTT as comfortable, increasing stability, and improving performance, the intervention exerted no considerable effects on all physiological and kinematic measures. KTT did alter neuromuscular recruitment, which has potential implications for injury prevention.

text: Physiological, kinematic, and electromyographic responses to kinesiology-type patella tape in elite cyclists Kinesiology-type tape (KTT) has become popular in sports for injury prevention, rehabilitation, and performance enhancement. Many cyclists use patella KTT; however, its benefits remain unclear, especially in uninjured elite cyclists. We used an integrated approach to investigate acute physiological, kinematic, and electromyographic responses to patella KTT in twelve national-level male cyclists. Cyclists completed four, 4-minute submaximal efforts on an ergometer at 100 and 200 W with and without patella KTT. Economy, energy cost, oxygen cost, heart rate, efficiency, 3D kinematics, and lower-body electromyography signals were collected over the last minute of each effort. Comfort levels and perceived change in knee stability and performance with KTT were recorded.

The effects of KTT were either unclear, non-significant, or clearly trivial on all collected physiological and kinematic measures. KTT significantly, clearly, and meaningfully enhanced vastus medialis peak, mean, and integrated electromyographic signals, and vastus medialis-to-lateralis activation. Electromyographic measures from biceps femoris and biceps-to-rectus femoris activation ratio decreased in either a significant or clinically meaningful manner. Despite most cyclists perceiving KTT as comfortable, increasing stability, and improving performance, the intervention exerted no considerable effects on all physiological and kinematic measures. KTT did alter neuromuscular recruitment, which has potential implications for injury prevention.

year: 2019

title: Recognising the negative impacts of aquatic weed management: Okawa Bay, Lake Rotoiti case study

authors: Scholes, Paul

abstract: The Te Arawa Rotorua Lakes Programme continues to implement measures to maintain and restore lake water quality in line with trophic level indices (TLI’s) for respective lakes. In Lakes Rotorua and Rotoiti this has also meant not only reducing nutrients to and in the lakes but also managing periodic cyano-bacterial (blue-green) algal blooms.
Restoration measures in the Rotorua and Rotoiti catchments have included land use management efforts to arrest nutrient inputs; diversion of Lake Rotorua waters from entering Rotoiti; sewage reticulation of lakeside communities; and treatment of inflows
with aluminium sulphate (alum). While restoration efforts have produced water quality gains in both lakes, in recent years, cyano-bacterial blooms have occurred in the shallow embayment of Lake Rotoiti, known as Okawa Bay.
These water quality gains have not come without a cost. Submerged aquatic weeds such as Hornwort are an increasing problem in the Rotorua Te Arawa Lakes and significant resources are needed to manage infestations primarily for aesthetic and recreational
amenity. Control of exotic aquatic weed is mostly with application of herbicide. Herbicide treatment leaves a decomposing biomass in the waterbody, potentially increasing the nutrient status.
We examine the impact aquatic weed decomposition has had on Okawa Bay’s nutrient status and the cyano-bacterial blooms over recent summers, and Bay of Plenty Regional Council’s response to reduce localised bloom development.

text: Recognising the negative impacts of aquatic weed management: Okawa Bay, Lake Rotoiti case study The Te Arawa Rotorua Lakes Programme continues to implement measures to maintain and restore lake water quality in line with trophic level indices (TLI’s) for respective lakes. In Lakes Rotorua and Rotoiti this has also meant not only reducing nutrients to and in the lakes but also managing periodic cyano-bacterial (blue-green) algal blooms.
Restoration measures in the Rotorua and Rotoiti catchments have included land use management efforts to arrest nutrient inputs; diversion of Lake Rotorua waters from entering Rotoiti; sewage reticulation of lakeside communities; and treatment of inflows
with aluminium sulphate (alum). While restoration efforts have produced water quality gains in both lakes, in recent years, cyano-bacterial blooms have occurred in the shallow embayment of Lake Rotoiti, known as Okawa Bay.
These water quality gains have not come without a cost. Submerged aquatic weeds such as Hornwort are an increasing problem in the Rotorua Te Arawa Lakes and significant resources are needed to manage infestations primarily for aesthetic and recreational
amenity. Control of exotic aquatic weed is mostly with application of herbicide. Herbicide treatment leaves a decomposing biomass in the waterbody, potentially increasing the nutrient status.
We examine the impact aquatic weed decomposition has had on Okawa Bay’s nutrient status and the cyano-bacterial blooms over recent summers, and Bay of Plenty Regional Council’s response to reduce localised bloom development.

year: 2015